“Strings, CFT & Integrability”

Fall Semester 2011

Wednesday, 14:00, HIT E41.1

Organised by: Niklas Beisert and Matthias Gaberdiel

day
date
time
venue
speaker
title
Wed
28.09.
14:00
HIT J52
Kewang Jin (ETH Zürich)
“Construction of Higher Spin Gravity in AdS from Collective Fields”
Wed
12.10.
14:00
HIT E41.1
Stefan Pfenninger (AEI Potsdam)
“Asymptotic W-symmetries in three-dimensional higher-spin gauge theories”
abstract (click to view) I review the Chern-Simons formulation of higher-spin (hs) gravity in D=2+1, the notion of AdS-asymptotic solutions and the idea of the corresponding asymptotic symmetry algebra. The connection to the Drinfeld-Sokolov reduction allows to find a method to systematically compute the asymptotic symmetry algebra of generic 3-dim bosonic hs gauge theories in a Virasoro-primary basis. I show how to apply this procedure to a one-parameter family of hs theories with infinitely many higher spin fields that is of crucial importance in the recently conjectured AdS-dual for minimal models by Gaberdiel and Gopakumar. (click to hide)
Wed
19.10.
14:00
HIT E41.1
Andrea Campoleoni (AEI Potsdam)
“Higher spins in D=2+1 and beyond”
abstract (click to view) In spite of the lack of local propagating degrees of freedom, three-dimensional gauge theories involving higher-rank tensors are interesting toy models for higher-spin interactions. I will review how these models surpass the no-go theorems against higher-spin interactions and I will compare them with Vasiliev's theory. It already provides interacting field equations for an infinite tower of higher-spin particles in (A)dS backgrounds of arbitrary dimension, but I will discuss how the hints coming from three-dimensional toy models could improve our understanding of exact solutions and higher-spin geometry. (click to hide)
Wed
26.10.
14:00
HIT E41.1
Tom Hartman (IAS Princeton)
“Holography in de Sitter Space with Higher Spin Gravity”
Wed
02.11.
14:00
HIT E41.1
Shailesh Lal (HRI Allahabad)
“Higher-Spin Theories in Odd Dimensions”
abstract (click to view) We describe aspects of Higher-Spin theories in odd (specifically 3 and 5) dimensions. We first discuss the deformation of D=3 higher-spin theories by a topological mass term and provide evidence that the dual CFT is logarithmic. We then go on to compute the one-loop partition function of the higher-spin fields in AdS_5 and compare with the boundary spectrum. Central to these results are the heat kernel expressions for arbitrary-spin particles in AdS, which we shall review. (click to hide)
Wed
09.11.
14:00
HIT E41.1
Song He (AEI Potsdam)
“Super Wilson loops and anomalies in N=4 SYM”
abstract (click to view) In the first part of my talk, I will introduce the proposal of a null polygonal Wilson loop in full, non-chiral N=4 superspace, and the computation of its one-loop expectation values. In the second part, I will discuss the related idea of reconstructing scattering amplitudes/chiral Wilson loops in N=4 SYM by its superconformal "anomalies", and an all-loop recursion relation for the anomalies of infrared-safe quantities, such as remainder and ratio functions. (click to hide)
Wed
16.11.
14:00
HIT K52
Sebastien Leurent (ENS Paris)
“Non-linear integral equations for AdS/CFT spectrum”
abstract (click to view) An important testable prediction of the AdS5/CFT4 duality is that the energy spectrum of type IIB strings in an AdS5xS5 background can be matched with the anomalous dimensions of operators in the 4-dimensional N = 4 Super-Yang-Mills theory. This predictions is all the more powerful, but also the harder to check, as it is a duality between strong and weak coupling. In the recent years a system of equations (the so-called Y-stem) was proposed to describe this energy spectrum, and was efficiently checked against string theory and gauge theory computations. This talk will introduce and motivate this Y-system, and sketch recent progress regarding its understanding from group-theoretical considerations and analyticity constraints, as well as its recasting into a finite set of nonlinear integral equations. (click to hide)
Wed
23.11.
14:00
HIT E41.1
Gleb Arutyunov (Utrecht ITP)
“The mirror TBA”
abstract (click to view) The mirror Thermodynamic Bethe Ansatz (TBA) is a tool to determine the spectrum of the AdS_5 x S^5 superstring and, through the gauge-string correspondence, the spectrum of conformal dimensions of composite primary operators in the planar maximally supersymmetric Yang-Mills theory. After reviewing a general construction of the mirror TBA, I will concentrate on its particular aspects which include symmetries and the description of string excitations with complex momenta. (click to hide)
Fri
02.12.
14:00
HIT E41.1
Cristian Vergu (ETH Zürich)
“Recent Progress in N=4 Super-Yang-Mills Scattering Amplitudes”
abstract (click to view) I will review recent progress in the computation of N=4 scattering amplitudes. (click to hide)
Wed
07.12.
14:00
HIT E41.1
Grigory Vartanov (DESY Hamburg)
“From 4d superconformal indices to 3d partition functions”
abstract (click to view) The recent progress in understanding of three-dimensional Seiberg dualities for supersymmetric field theories based on the calculation of exact quantities such as superconformal indices and partition functions is discussed. It is shown that equality of superconformal indices for any four-dimensional pair of dual supersymmetric theories reduces to the number of equalities of partition functions for three-dimensional supersymmetric theories thus giving the whole set of three-dimensional dualities (both for CS and SYM theories) from one "parent" dual pair in four dimensions. Connections of the reduced superconformal indices of four-dimensional theories with the state integrals of the knot theory and the two-dimensional vortex partition function are also described. (click to hide)
Wed
14.12.
14:00
HIT E41.1
Marius de Leeuw (ETH Zürich)
“Integrable deformations of the AdS5 superstring”
abstract (click to view) In this talk we will discuss deformations of the AdS5 superstring that preserve integrability. These deformations are obtained by inserting so-called twists in the transfer matrix for the undeformed model. We will discuss the Bethe equations and explain how to describe finite size corrections using Lüscher's approach and the TBA. In particular we will focus on the spectrum of gamma-deformed theories and orbifold models. (click to hide)
Wed
21.12.
14:00
HIT E41.1
Constantin Candu (ETH Zürich)
“Exactly marginal fields in G/H conformal field theories”
abstract (click to view) I am going to talk about exactly marginal fields in non-unitary two dimensional conformal field theories such as sigma models on symmetric spaces and Goddard-Kent-Olive type cosets. I will be mostly concerned with their origin, classification and the importance they have in uncovering dualities. (click to hide)

last modified: Wed, 9 Apr 2014, 11:38 CEST

Spring Semester 2012

Wednesday, 14:00, HIT E41.1

Organised by: Niklas Beisert and Matthias Gaberdiel

day
date
time
venue
speaker
title
Wed
21.03.
14:00
HIT E41.1
Jan Manschot (Uni Bonn)
“BPS invariants of rational surfaces”
Wed
04.04.
14:00
HIT E41.1
Sakura Schaefer-Nameki (Kings College London)
“GUTs and Geometry” (cancelled)
Fri
20.04.
17:15
HG F30
Niklas Beisert (ETH Zürich)
Einführungsvorlesung: “Teilchenphysik, Stringtheorie und Magnetismus” (in German)
Wed
25.04.
14:00
HIT E41.1
Tristan McLoughlin (AEI Potsdam)
“New dualities in three-dimensional scattering amplitudes”
Wed
09.05.
14:00
HIT E41.1
Till Bargheer (Uppsala)
“Holographic Three-Point Functions in N=4 SYM”
Wed
16.05.
14:00
HIT E41.1
Samuel Beliard (Montpellier 2)
“Manin triples twist and co-ideal algebras”
abstract (click to view) The algebraic structures that lead to the integrability of quantum integrable models are given by quantum groups (for models on a line or on a circle) and by coideal algebras (for models on a segment or on a half-line). Quantum groups can be constructed from the quantification of Universal enveloping Lie algebras. This procedure, introduced by Drinfel'd in 1985, uses the notion of bialgebras or equivalently of Manin triples. In a resent paper, (arxiv:1202.2312 in collaboration with N. Crampé) we introduced the notion of Manin triples twist and gave a procedure to construct coideal algebras from Universal enveloping Lie sub-algebras. We will review Drinfel'd quantification procedure and present our quantification procedure to obtain coideal algebras. Some applications to quantum integrable models will be discussed. (click to hide)
Wed
23.05.
14:00
HIT E41.1
Kyriakos Papadodimas (CERN)
t.b.a.
Wed
27.06.
14:00
HIT E41.1
Rudranil Basu (SN Bose Center, Kolkata)
“Finite 3d de-Sitter Quantum Gravity”

last modified: Thu, 10 Apr 2014, 14:56 CEST

Fall Semester 2012

Wednesday, 14:00, HIT E41.1

Organised by: Niklas Beisert and Matthias Gaberdiel

day
date
time
venue
speaker
title
Wed
03.10.
14:00
HIT E41.1
Thomas Creutzig (Darmstadt)
“Modular Data of affine sl(2) at admissible level”
abstract (click to view) One of the main problems in logarithmic CFT is the Verlinde formula. Especially in the case of WZW models at fractional level this formula seemed not to work properly. The main part of this talk will be concerned with the example of affine sl(2) at the admissible level -1/2. I want to explain how various problems concerning the spectrum and characters can be solved and that the Verlinde formula actually works very nicely. Finally, I will point out generalizations to other admissible level theories and similar patterns with other classes of logarithmic CFT. (click to hide)
Wed
17.10.
14:00
HIT E41.1
Johannes Broedel (ETH Zürich)
“Color constraints on string effective actions”
Wed
31.10.
14:00
HIT E41.1
Marcus Spradlin (Brown University & CERN)
“The Symbology of Scattering Amplitudes”
Wed
07.11.
14:00
HIT E41.1
Rutger Boels (Hamburg)
“Cancellations in perturbative quantum gravity theories from color-kinematic duality”
Wed
14.11.
14:00
HIT E41.1
Dieter Luest (LMU & MPI Munich)
“Strings and (Non)-Geometry”
abstract (click to view) In this talk I discuss the relation between strings and (non)-geometry. Due to stringy symmetries, stringy geometry goes beyond standard Riemannian geometry. We show that the corresponding non-geometric backgrounds can be described by non-commutative or even non-associative algebras. (click to hide)
Wed
28.11.
14:00
HIT E41.1
Ralph Blumenhagen (MPI Munich)
“Non-geometric strings and the differential geometry of Lie algebroids”
Wed
05.12.
14:00
HIT E41.1
Sakura Schaefer-Nameki (King's College London)
“GUTs and Geometry”
abstract (click to view) In recent years, F-theory has emerged as an ideal framework for building supersymmetric Grand Unified Theories within string theory. The geometry of singular elliptically fibered Calabi-Yau manifolds plays a key role in this approach. I will explain this connection as well as recent progress on phenomenological aspects of F-theory GUTs. (click to hide)
Wed
12.12.
14:00
HIT E41.1
Eric Perlmutter (Cambridge)
“Probing higher spin black holes”

last modified: Wed, 9 Apr 2014, 11:38 CEST

Spring Semester 2013

Wednesday, 14:00, HIT E41.1

Organised by: Niklas Beisert and Matthias Gaberdiel

day
date
time
venue
speaker
title
Wed
27.02.
14:00
HIT E41.1
Florian Loebbert (Niels Bohr International Academy)
“Spin Chains and Scattering Amplitudes in N=4 SYM Theory”
Wed
13.03.
14:00
HIT E41.1
Yacine Ikhlef (LPTHE Paris)
“Discrete holomorphic parafermions and quantum groups”
abstract (click to view) Yacine Ikhlef (LPTHE Paris)
Discrete holomorphic parafermions and quantum groups
hide abstract»
Discrete holomorphic parafermions are lattice operators in a 2d statistical model, which satisfy a discrete version of the Cauchy-Riemann equations. It has been observed in many examples that these objects appear exactly at the integrable values of the Boltzmann weights. We give a general explanation of this observation, by relating discrete parafermions to non-local conserved currents in quantum-group invariant theories constructed in [D. Bernard and G. Felder, Nucl. Phys. B365, 98 (1991)]. This is joint work with R. Weston (Edinburgh), M. Wheeler and P. Zinn-Justin (LPTHE). (click to hide)
Thu
14.03.
13:30
HIT E41.1
Shouvik Datta (Bangalore)
“Aspects of classical solutions in Chern-Simons higher spin supergravity”
abstract (click to view) We construct and study conical defects and black holes in Chern-Simons supergravity based on the superalgebra sl(N|N-1). For this case of N=3, we solve Killing spinor equations explicitly. We show that for the general sl(N|N-1) theory the condition for the periodicity of the Killing spinor can be written in terms of the products of the odd roots of the superalgebra and the eigenvalues of the holonomy matrix of the background. This is verified for conical defects in the N=3 theory. We also find that smooth supersymmetric conical defects exist for N \geq 4. We then study higher spin black hole solutions embedded in the superalgebra sl(3|2). Using the relation between the bulk field equations and the Ward identities of a CFT with N=2 super W_3 symmetry, we identify the bulk charges and chemical potentials with that of the boundary CFT. These identifications indicate that the black hole solutions with R-symmetry charges are spectrally flowed solutions of the higher spin black hole with only spin 3 hair. The entropy of the R-charged black hole is then written in terms of the both the bulk charges and that of the boundary. (click to hide)
Thu
28.03.
16:00
HIT E41.1
Abhishek Chowdhury (HRI Allahabad)
“Black hole bound state metamorphosis”
Mon
08.04.
16:45
Irchel Y16G05
Anastasia Volovich (Brown University & CERN)
Theoretical Physics Colloquium: “Hidden Structures of Scattering Amplitudes”
abstract (click to view) I will review some of the remarkable progress in recent years on unlocking the hidden structures of particle scattering amplitudes, and on the application of these insights to help make some previously impossible calculations possible. (click to hide)
Wed
10.04.
16:45
HPV G4
Marcus Spradlin (Brown University & CERN)
Zurich Physics Colloquium: “The Remarkable Mathematical Structure of Scattering Amplitudes”
abstract (click to view) Perhaps no area of physics is more notorious for its very difficult and tedious calculations than quantum field theory. Yet such computations are of crucial importance: as we spend billions of euros on high energy particle experiments, it is an embarrassment when data analysis is hampered by the difficulty to carry out what should be “textbook” computations. I will review for a general audience some of the remarkable mathematical insights which have led in the past decade to a revolution in our understanding of scattering amplitudes in quantum field theory, as well as to wizardry which has helped make some previously impossible computations completely trivial. (click to hide)
Wed
15.05.
14:00
HIT E41.1
Stefano Cremonesi (Imperial College London)
“2d N=(2,2) Supersymmetry and Localisation” (cancelled)
Wed
29.05.
14:00
HIT E41.1
Tomasz Łukowski (HU Berlin)
“Harmonic R-matrices for Scattering Amplitudes and Spectral Regularization”

last modified: Wed, 9 Apr 2014, 11:38 CEST

Fall Semester 2013

Tuesday, 11:00, HIT E41.1

Organised by: Niklas Beisert and Matthias Gaberdiel

day
date
time
venue
speaker
title
Tue
01.10.
11:00
HIT E41.1
Hadi Godazgar (U. Cambridge)
“Generalised geometry of D=11 supergravity”
abstract (click to view) In this talk I will motivate the need for a reformulation of D=11 supergravity that emphasises structures that appear upon toroidal reduction reduction of D=11 supergravity to four dimensions. I will explain how all bosonic fields in eleven dimensions can be associated with E7 objects and stress the utility of this reformulation in terms of its direct relation to D=4 gauged supergravities. (click to hide)
Tue
08.10.
11:00
HIT E41.1
Cheng Peng (ETH Zürich)
“Dualities from higher-spin supergravity”
Tue
15.10.
11:00
HIT E41.1
Tristan Dennen (NBI Copenhagen)
“The Ultraviolet Structure of N=4 Supergravity”
Tue
29.10.
11:00
HIT E41.1
Juan Jottar (U. Amsterdam)
“Aspects of higher spin AdS(3)/CFT(2)”
Tue
12.11.
14:00
HIT E41.1
Piotr Tourkine (IPhT Saclay)
“Tropical Amplitudes”
Tue
19.11.
14:00
HIT E41.1
Adolfo Guarino (Bern)
“Some aspects of new maximal supergravity”
Mon
02.12.
16:45
Irchel Y16G05
Hubert Saleur (IPhT Saclay & UCLA)
Theoretical Physics Colloquium: “Charge transmutation in the fractional quantum Hall effect – quantum field theory meets nano electronics”
Tue
10.12.
11:00
HIT E41.1
Marco Baggio (ETH Zürich)
“Conformal Symmetry for Black Holes in Four Dimensions and Irrelevant Deformations”
Tue
17.12.
11:00
HIT E41.1
David Skinner (U. Cambridge)
“Twistor Strings for N=8 Supergravity”

last modified: Wed, 9 Apr 2014, 11:39 CEST

Spring Semester 2014

Tuesday, 14:00, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel and Jan Plefka

day
date
time
venue
speaker
title
Wed
05.03.
16:45
HPV G4
Jan Plefka (Humboldt Universität zu Berlin / ETH Zürich)
Physics Colloquium: “Scattering Amplitudes and Hidden Symmetries”
abstract (click to view) An introduction to gauge field theory – the underlying theoretical framework of elementary particle physics – and its symmetries will be given. Then we shall discuss supersymmetry and a holographic description of gauge fields in terms of a higher dimensional string theory known as the AdS/CFT correspondence. Finally, we focus on recent results for scattering amplitudes in supersymmetric gauge theory, their string dual description and surprising hidden symmetries pointing towards an integrable structure. (click to hide)
Tue
11.03.
14:00
HIT E41.1
Takashi Kameyama [亀山尚史] (Kyōto University)
“Infinite-dimensional non-local symmetries of Jordanian deformed Landau-Lifshitz sigma models”
Tue
18.03.
12:30
HIT E41.1
Evgeny Skvortsov (AEI Potsdam)
“Higher-spin symmetry in AdS and CFT”
abstract (click to view) I will discuss the implications of extended symmetries in higher dimensional CFT's and show that the algebra they generate, the higher-spin algebra, is unique (which extends Maldacena-Zhiboedov results) apart from the 4d case where one finds a one-parameter family. As an infinite-dimensional extension of conformal symmetries higher-spin algebras can be used to restrict correlation functions and I will present an explicit formula that computes all correlators in unbroken Vasiliev higher-spin theory. (click to hide)
Tue
25.03.
14:00
HIT E41.1
Balt van Rees (CERN)
“The superconformal bootstrap program”
Tue
15.04.
14:00
HIT J53
Dmitry Chicherin (LAPTH Annecy)
“Yang-Baxter operators and scattering amplitudes in N=4 super-Yang-Mills theory”
abstract (click to view) During past years plenty of unexpected symmetries have been revealed in the structure of perturbative scattering amplitudes. We formulate Yangian symmetry of amplitudes in N=4 super Yang-Mills theory in terms of eigenvalue relations for monodromy matrix operators. The Quantum Inverse Scattering Method provides us the appropriate tools to treat the extended symmetry and to recover as its consequences many known features like cyclic symmetry, BCFW recursion, Inverse Soft Limit construction, Grassmannian integral representation, R-invariants and on-shell diagram approach. (click to hide)
Tue
29.04.
14:00
HIT E41.1
Henrik Johansson (CERN)
“Pure Gravities via Color-Kinematics Duality for Fundamental Matter”
Tue
06.05.
14:00
HIT E41.1
Joseph Minahan (Uppsala University)
“Three-point functions for short operators at strong coupling”
abstract (click to view) Using the AdS/CFT correspondence we compute the three-point structure constants for primary operators in planar N=4 super Yang-Mills at strong coupling. The computation involves finding the relevant vertex operators for the massive string states dual to the operators and then computing their three-point string amplitudes. (click to hide)
Thu
08.05.
15:15
HG G43
Jörg Teschner (DESY Hamburg)
Talks in Mathematical Physics: “Conformal blocks for non-rational CFT”
abstract (click to view) We revisit the representation-theoretic definition of
the Virasoro conformal blocks. This construction yields
infinite-dimensional vector spaces in general. Our goal
will be to explain how to define bases for interesting
topological subspaces of the spaces of conformal blocks
by means of the gluing construction. This yields a
first example where the Friedan-Shenker program can
be realized for a non-rational conformal field theory. (click to hide)
Tue
13.05.
14:00
HIT J53
Guillaume Bossard (École Polytechnique Paris)
“On supergravity effective actions”
Tue
20.05.
14:00
HIT E41.1
James Drummond (Southampton / CERN)
“Hexagon functions and scattering amplitudes in N=4 super Yang-Mills theory”
Tue
27.05.
14:00
HIT E41.1
Stefano Cremonesi (Imperial College London)
“Two-dimensional N=(2,2) supersymmetry in curved space”
abstract (click to view) Over the last few years, localisation techniques have led to a host of exact results for supersymmetric quantum field theories defined on curved spaces of various dimensions. In this context, N=(2,2) supersymmetric field theories in two dimensions are particularly interesting in view of their relation to superstrings on Calabi-Yau manifolds. In this talk I will review the general formulation of d=2 N=(2,2) supersymmetric field theories with a vector-like U(1) R-symmetry in curved space. I will discuss supersymmetric backgrounds on compact oriented Riemann surfaces, uplifts to backgrounds in higher dimensions, supersymmetric multiplets and Lagrangians in curved space. (click to hide)
Thu
03.07.
14:00
HIT K52
Chetan Krishnan (Bangalore)
“Spins and Strings on Cosmological Singularities”
abstract (click to view) Singularities are a challenge in string theory, and so are time-dependent backgrounds. So very little is known about singularities in time-dependent (cosmological) backgrounds. I will discuss how toy versions of the big bang singularity can be resolved in higher spin theories and how that can be related to aspects of string scattering amplitudes. (click to hide)
Tue
08.07.
14:00
HIT E41.1
Burkhard Schwab (Brown University)
“Soft factors in field and string theory”

last modified: Fri, 27 Jun 2014, 15:55 CEST

Fall Semester 2014

Tuesday, 11:30, HIT E41.1

Organised by: Niklas Beisert and Matthias Gaberdiel

day
date
time
venue
speaker
title
Tue
09.09.
14:00
HIT E41.1
Oliver Schlotterer (AEI Potsdam)
“The anatomy of one-loop amplitudes in pure spinor superspace”
abstract (click to view) I will describe a framework for ten-dimensional one-loop amplitudes involving
any number of massless states, both in superstring theory and its field theory
limit. The multiplets of gluons and gravitons are represented by superfields of
linearized ten-dimensional super Yang-Mills. Their external tree level
subdiagrams are encoded in multiparticle superfields from 1404.4986 whose
equations of motion generalize the single-particle case. BRST symmetry and zero
mode saturation of the pure spinor superstring strongly constrain the
composition rules for multiparticle fields and allows for a systematic
classification of BRST invariants as in 1408.3605. Examples will be given for
their appearance in string- and SYM amplitudes, along with worldsheet- and
Feynman integrals. (click to hide)
Fri
19.09.
14:00
HG G19.1
various
Talks in Mathematical Physics: “End of Summer Meeting 2014”
abstract (click to view) 14:00 – 14:45 Samuel Monnier, UZH, Finite higher spin symmetries
15:00 – 15:45 Marcello Porta, UZH, Mean-field evolution of fermionic systems
Tea
16:15 – 17:00 Junliang Shen, ETH, Cobordism invariants of the moduli space of stable pairs
17:15 – 18:00 Giovanni Felder, ETH, Presentation of SwissMAP and discussion (click to hide)
Wed
01.10.
14:00
HIT E41.1
Yang Zhang (ETH Zürich)
“Scattering amplitudes via computational algebraic geometry methods”
abstract (click to view) This talk is about multi-loop scattering amplitudes calculation via
computational algebraic geometry methods. We illustrate the difference between
one-loop and higher-loop unitarity, and argue why algebraic geometry methods are
necessary for multi-loop scattering amplitude computation. We demonstrate our
methods by examples from integrand reduction, maximal unitarity and
integration-by-parts identities. (click to hide)
Tue
07.10.
11:30
HIT E41.1
Juan Jottar (ETH Zürich)
“Semiclassical Chern-Simons description of deformed CFTs with extended symmetries”
Tue
14.10.
11:30
HIT K51
Shouvik Datta (Bangalore)
“Entanglement entropy in W-algebra CFTs and holography”
abstract (click to view) We consider conformal field theories in 1+1 dimensions with W-algebra symmetries and finite temperature and deformed by a chemical potential (\mu) for a higher spin current. Using OPEs and uniformization techniques, we show that the order \mu^2 correction to the Renyi and entanglement entropies (EE) of a single interval in the deformed theory is universal. This universal feature is also supported by explicit computations for the free fermion and free boson CFTs -- for which the EE is calculated by using the replica trick in conformal perturbation theory by evaluating correlators of twist fields with higher spin operators. Furthermore, the holographic EE proposal is verified by obtaining the same correction to EE from Wilson lines in higher spin gravity.
We then examine relative entropy in the context of higher-spin holography. We confirm the expected short-distance behaviour of relative entropy from holography. This is done by showing that the difference in the modular Hamiltonian between a high-temperature state and the vacuum matches with the difference in the entanglement entropy in the short-distance regime. (click to hide)
Tue
21.10.
11:30
HIT E41.1
Jie Gu (Bonn University)
“Knot invariants, WZW models, and quantum groups”
Tue
28.10.
11:30
HIT E41.1
Andrei Babichenko (Weizmann Institute)
“Classical and quantum integrability of string on AdS₃ × S³ × T⁴ with mixed flux”
Wed
29.10.
11:30
HIT E41.1
Karan Govil (Pennsylvania State University)
“Aspects of Higher Spin Symmetries in Various Dimensions”
abstract (click to view) The algebras of higher spin symmetries in conformal field theories in four and six dimensions are not unique and have a richer structure due to the existence of infinite short multiplets besides the usual scalar and spinor. We will focus on recent results that show there exists a one parameter family (continuous of d=4 and discrete for d=6) of higher spin algebras and superalgebras, and give an explicit unitary representation for these algebras using quasiconformal methods. We will also discuss the implications of these results for the AdS5/CFT4 and AdS7/CFT6 higher spin holography. (click to hide)
Tue
11.11.
11:30
HIT E41.1
Angnis Schmidt-May (Stockholm University)
“Classically Consistent Theories of Interacting Spin-2 Fields”
Tue
18.11.
11:30
HIT K51
Martin Sprenger (ETH Zürich)
“High-Energy Scattering in strongly coupled N=4 super Yang-Mills”
Wed
19.11.
11:30
HIT E41.1
Justin David (Bangalore)
“Renyi entropies of free bosons on the torus and holography”
abstract (click to view) We analytically evaluate the Renyi entropies for the two dimensional free
boson CFT. The CFT is considered to be compactified on a circle and at
finite temperature. The Renyi entropies S_n are evaluated for a single
interval using the two point function of bosonic twist fields on a torus.
For the case of the compact boson, the sum over the classical saddle
points results in the Riemann-Siegel theta function associated with the
A_{n-1} lattice. We then study the Renyi entropies in the
decompactification regime.
We show that in the limit when the size of the interval becomes the size
of the spatial circle, the entanglement entropy reduces to the thermal
entropy of free bosons on a circle. We then set up a systematic high
temperature expansion of the Renyi entropies and evaluate the finite size
corrections for free bosons. Finally we compare these finite size
corrections both for the free boson CFT and the free fermion CFT with the
one-loop corrections obtained from bulk three dimensional handlebody
spacetimes which have higher genus Riemann surfaces as its boundary.
By evaluating these corrections both in the bulk and in the CFT explicitly
we show that they precisely agree. (click to hide)
Tue
25.11.
11:30
HIT E41.1
Matthias Wilhelm (HU Berlin)
“Amplitudes, Form Factors and the Dilatation Operator of N=4 SYM Theory”
abstract (click to view) Farm factors form a bridge between the purely off-shell correlation
functions and the purely on-shell amplitudes. In this talk, we study the
form factor of a generic gauge-invariant local composite operator in N=4
SYM theory. At tree-level and for a minimal number of external fields, the
form factor exactly realises the spin-chain picture of N=4 SYM theory in
the language of scattering amplitudes. Via generalised unitarity, we
obtain the cut-constructible part of the one-loop correction to the
minimal form factor of a generic operator. Its UV divergence yields the
complete one-loop dilatation operator of the theory. Preceding to the next
loop order, we compute the complete two-loop correction to the two-point
form factor of the Konishi operator via unitarity and obtain the two-loop
Konishi anomalous dimensions from it. For the Konishi operator as well as
other non-protected operators, important subtleties arise which require an
extension of the method of unitarity. The talk is based on the recent
works 1410.6309 and 1410.8485. (click to hide)
Tue
09.12.
11:30
HIT E41.1
Mario Martone (University of Cincinnati)
“Classification of Rank 1 N=2 superconformal field theories from deformation of Kodaira singularities”
abstract (click to view) The low energy effective actions on the Coulomb branch of rank 1 N=2
superconformal field theories (SCFTs) in four dimensions are described by
the Kodaira classification of singular degenerations of one-dimensional
families of elliptic curves. Evidence from conjectured S-dualities
indicates that most of these singular families has more than one
inequivalent mass deformation, corresponding to inequivalent SCFTs. We
construct many examples of inequivalent deformations of the Kodaira
singularities preserving N=2 supersymmetry, reproducing all the ones
predicted by S-duality and conjecture many more. (click to hide)
Wed
10.12.
14:00
HIT K51
Mads Søgaard (Niels Bohr Institute)
“Leading Singularities of the ABDK Relation & Elliptic Functions and Maximal Unitarity”
abstract (click to view) This talk consists of two parts. In the first part we reconstruct the ABDK
relation from maximal and near-maximal cuts of one- and two-loop integrals
with
up to five external legs. The underlying phenomenon is that several integrals
can have kinematical support on the same generalized unitarity cut across loop
order. In the second part of the talk we show how to analytically derive
unique
projectors for two-loop integrals with internal masses. Our method is based on
multivariate residues and Weierstrass’ elliptic functions. (click to hide)
Tue
16.12.
11:30
HIT K52
Mikhail Isachenkov (DESY Hamburg)
“Chiral Ring of Strange Metals”
abstract (click to view) A candidate description for a strange metal phase in 1+1 dimensions,
namely a model of strongly-coupled fermions in the adjoint representation of
SU(N) is considered. It is known that such models at high densities flow
to IR WZNW theories having an emergent (2,2) supersymmetry.
I describe the chiral ring of such theories and discuss its large N limit. (click to hide)

last modified: Wed, 7 Jan 2015, 17:04 CET

Spring Semester 2015

Wednesday, 11:30, HIT E41.1

Organised by: Niklas Beisert and Matthias Gaberdiel

day
date
time
venue
speaker
title
Wed
25.02.
11:30
HIT E41.1
Georgios Papathanasiou (LAPTh Annecy)
“A Symbol of Uniqueness: The Cluster Bootstrap for the 3-Loop MHV Heptagon”
abstract (click to view) Seven-particle scattering amplitudes in planar super-Yang-Mills theory are
believed to belong to a special class of generalised polylogarithm
functions called heptagon functions. These are functions with physical
branch cuts whose symbols may be written in terms of the 42 cluster
A-coordinates on Gr(4,7). Motivated by the success of the hexagon bootstrap
programme for constructing six-particle amplitudes we initiate the
systematic study of the symbols of heptagon functions. We find that there
is exactly one such symbol of weight six which satisfies the MHV last-entry
condition and is finite in the 7 || 6 collinear limit. This unique symbol
is both dihedral and parity-symmetric, and remarkably its collinear limit
is exactly the symbol of the three-loop six-particle MHV amplitude,
although none of these properties were assumed a priori. It must therefore
be the symbol of the three-loop seven-particle MHV amplitude. The
simplicity of its construction suggests that the n-gon bootstrap may be
surprisingly powerful for n > 6. (click to hide)
Wed
04.03.
11:30
HIT E41.1
Noppadol Mekareeya (CERN)
“Coulomb branch and the moduli space of instantons”
abstract (click to view) I will explain how to compute the Hilbert series that counts chiral operators parametrising the Coulomb branch of the moduli space of 3d N=4 supersymmetric field theories. The formula has applications to physics, such as to the study of infrared dualities in three dimensions and of backgrounds with eight supercharges, as well as to mathematics, where it provides a new way to characterise hyperKähler cones as algebraic varieties. I will then show how the Coulomb branch of certain 3d N=4 generalised quiver gauge theories can be used to compute the Hilbert series of the moduli space of k G-instantons, for any simple Lie group G. The construction is alternative to the ADHM construction that is only available for classical groups G. (click to hide)
Wed
11.03.
11:30
HIT K 52
Blagoje Oblak (ULB Brussels)
“BMS Symmetry in Three Dimensions”
abstract (click to view) In this talk I will sketch the relation between unitary representations of the BMS3 group and three-dimensional asymptotically flat gravity. More precisely, I will first review the theory of induced representations for semi-direct product groups, before giving an exact definition for the BMS group in 3D and showing that its induced representations are classified by coadjoint orbits of the Virasoro group. This will lead to the sought-for relation between representations of BMS3 and gravity in 3D flat space. Finally, I will show how one can compute characters associated with induced representations. Applying this computation to the BMS3 group turns out to produce one-loop partition functions of gravity around 3D thermal flat space. (click to hide)
Wed
01.04.
11:30
HIT E41.1
Eduardo Casali (DAMTP Cambridge)
“The scattering equations beyond tree-level”
abstract (click to view) The scattering equations are a new way to encode the kinematical properties
of massless particle scattering. This has led to new, compact
representations of field theory scattering amplitudes, where the sum over
Feynman diagrams is traded by a constrained integral over the moduli space
of Riemann surfaces. The majority of the work done on the scattering
equations has dealt with their tree-level form, and consequently to
tree-level field theory amplitudes. In this talk I'll discuss the extension
of this framework to loop-level. This is done using the ambitwistor string
which is a chiral 2D CFT which provides a first principle derivation of the
scattering equations as well as several of the new formulas for the
amplitudes. I'll introduce the generalization of the scattering equations
to any loop-level and give factorization arguments for their validity, with
explicit examples at one and two loops. (click to hide)
Wed
22.04.
11:30
HIT E41.1
Riccardo Borsato (Utrecht University)
“Deforming AdS5 x S5”
abstract (click to view) I will discuss the so-called "eta-deformation" of strings on AdS5 x S5. This is particularly interesting since it preserves the classical integrability of the original theory and it realises a q-deformation of its symmetry algebra. In addition to the deformed metric also a B-field is generated, and a singularity appears at a finite radius of the deformed AdS space. I will explain how we confirmed the q-deformation by matching the tree-level scattering on the worldsheet with the large-tension limit of the S-matrix previously found by requiring psu_q(2|2) invariance. I will also address the challenging question of whether we can embed the metric and B-field into a full type IIB supergravity background. This will be done by computing the deformed Lagrangian at quadratic order in fermions and by addressing the novel puzzles introduced by the deformation procedure. (click to hide)
Wed
06.05.
11:30
HIT E41.1
Axel Kleinschmidt (AEI Potsdam)
“Instanton corrections in string theory and degenerate Whittaker vectors”
abstract (click to view) U-duality and supersymmetry in toroidally compactified string theory
put strong constraints on scattering amplitudes. The solutions to these
constraints can be automorphic forms on the moduli space of compactifications.
Since U-duality connects strong and weak coupling physics it is possible to
extract non-perturbative information from these automorphic forms. I will review
recent results and methods for this analysis. (click to hide)
Wed
13.05.
11:30
HIT E41.1
Arthur Lipstein (DESY Hamburg)
“Soft Theorems from Conformal Field Theory”
abstract (click to view) It has recently been suggested by Strominger and collaborators that the soft
theorems for Yang-Mills and gravity amplitudes can be interpreted as Ward
identities of a 2d CFT at null infinity. In this talk, I will derive the soft
theorems using a 2d CFT known as ambitwistor string theory, which describes 4d
Yang-Mills and gravity with any amount of supersymmetry. I will also describe
how the algebra of soft limits can be encoded in the braiding of soft vertex
operators, and compute 1-loop corrections to the subleading soft graviton
theorem by considering ambitwistor string theory on a genus one worldsheet. (click to hide)
Wed
20.05.
11:30
HIT E41.1
Bruno Le Floch (ENS Paris)
“AGT correspondence for surface operators”
abstract (click to view) With Jaume Gomis, we consider M2 branes ending on a stack of
M5 branes. Compactified on a Riemann surface C, the stack of M5
branes yields a 4d N=2 gauge theory, and M2 branes insert a half-BPS
surface operator. The AGT correspondence equates the sphere partition
function of the 4d theory to a CFT correlator on C, and the surface
operator translates to an extra local insertion on C. From the
correspondence we deduce a 2d N=(2,2) gauge theory description of the
surface operator, hence of the M2--M5 intersection. We also find 2d
N=(2,2) analogues of Seiberg duality. (click to hide)
Wed
27.05.
11:30
HIT E41.1
Vladimir Mitev (HU Berlin)
“Toda 3-Point Functions From Topological Strings”
abstract (click to view) We consider the long-standing problem of obtaining the 3-point functions of Toda CFT. Our main tools are topological strings and the AGT-W relation between gauge theories and 2D CFTs. Using the refined topological string formalism, we obtain the 5D partition functions for the T_N theories and provide the exact AGT-W dictionary that relates them to the Toda structure constants. Using a procedure known as Higgsing, we manage to obtain the formula of Fateev and Litvinov for the Toda structure constants with one semi-degenerate primary field. (click to hide)
Fri
03.07.
14:00
HIT K51
Ricardo Medina (Universidade Federal de Itajubá)
“Revisiting the S-matrix approach to the open superstring low energy effective lagrangian”

last modified: Fri, 10 Jul 2015, 14:12 CEST

Fall Semester 2015

Wednesday, 11:30, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel and Christoph Keller

day
date
time
venue
speaker
title
Wed
30.09.
11:30
HIT E41.1
Alessandro Sfondrini (ETH Zürich)
“Integrability for AdS3/CFT2”
Wed
14.10.
11:45
HIT K51
Kallol Sen (Indian Institute of Science, Bangalore)
“Analytic bootstrap for operators with large spin”
abstract (click to view) Large spin operators manifest themselves in the Lightcone limit of bootstrap equation for four scalar operators. We consider such large spin operators and analyze how the twist changes if we add a stress tensor to the spectrum. Observe that the correction to the twist of these operators depends crucially on the presence of the stress tensor in a particular way. In some limit when the spin of these operators is much larger than the twist of these operators, the correction (anomalous dimensions) match with the holographic predictions. We also observe some more interesting facts about these anomalous dimensions. (click to hide)
Tue
20.10.
13:00
HIT E41.1
Yang Lei (Durham)
Journal Club: “Towards non-AdS Higher Spin Theory in d≥3”
Wed
21.10.
11:30
HIT E41.1
Shouvik Datta (ETH Zürich)
“Universal features of left-right entanglement entropy”
abstract (click to view) We show the presence of universal features in the entanglement entropy of regularized boundary states for (1+1)-d CFTs on a circle when the reduced density matrix is obtained by tracing over right/left-moving modes. We derive a general formula for the left-right entanglement entropy in terms of the central charge and the modular S matrix of the theory. When the state is chosen to be an Ishibashi state, this measure of entanglement is shown to precisely reproduce the spatial entanglement entropy of a (2+1)-d topological quantum field theory. This result follows as a consequence of the TQFT/CFT correspondence. (click to hide)
Wed
28.10.
11:45
HIT K51
Johannes Noller (University of Oxford)
“Consistent graviton theories”
abstract (click to view) There has been a lot of progress recently in understanding what consistent graviton theories can be built in an effective field theory sense. This has led to the discovery of new graviton kinetic terms, potential interactions and ways of coupling matter to gravity. I will review and present this graviton theory space for local and Lorentz invariant theories. Along the way I will point out applications to cosmology, related discoveries of new dualities and symmetries, highlight which bits of theory space we already know to be unique and where there is still uncharted territory. (click to hide)
Wed
04.11.
11:30
HIT E41.1
Stefan Theisen (AEI Potsdam)
“Anomalies and Conformal Manifolds”
abstract (click to view) The two-point function of exactly marginal operators leads to a universal contribution to the trace anomaly in even dimensions. We study aspects of this trace anomaly, emphasizing its interpretation as a sigma model, whose target space M is the space of conformal field theories. When the underlying conformal field theory is supersymmetric, this leads to new information about the conformal manifolds of these theories. For N = (2, 2) theories in d = 2 and N = 2 theories in d = 4 we show that the relation between the sphere partition function and the Kahler potential of M follows immediately from the appropriate sigma models that we construct. (click to hide)
Tue
10.11.
12:50
HIT K51
Michael Gutperle (UCLA)
Journal Club: “Entanglement entropy of Wilson surfaces from bubbling geometries in M-theory”
Wed
11.11.
11:30
HIT E41.1
Sunil Mukhi (Pune)
“Modular Invariance and Entanglement Entropy”
Mon
16.11.
16:45
HIT H42
Marcos Mariño (University of Geneva)
Theory Colloquium: “Strings from Random Matrices and Quantum Gases”
Wed
25.11.
11:30
HIT E41.1
Diego Hofman (University of Amsterdam)
“Geometry, Modularity and Entanglement in WCFT”
abstract (click to view) Warped Conformal Theories (WCFTs) are 2 dimensional non
relativistic theories with enough structure to obtain exact results of
comparable power to usual 2 dimensional CFTs. As they are non-relativistic they
do not couple naturally to Riemannian geometry but, instead, to a particular
version of Newton-Cartan geometry. The study of these geometric features is of
great importance as it sheds light on the meaning of Holography away from AdS
spaces and it allows for the extension of concepts like modular invariance to a
non-relativistic setup. Furthermore, we can obtain exact results like
entanglement entropies using these tools. These models might also illuminate the
path to a fully covariant formalism for CFTs with an extended W_N algebra. (click to hide)
Wed
25.11.
14:00
HIT E41.1
Karthik Inbasekar (TIFR Mumbai)
“2 → 2 scattering in supersymmetric matter Chern-Simons theories at large N”
abstract (click to view) Non-abelian Chern-Simons theories are very rich. When coupled to matter in
the fundamental representation of U(N), these theories are exactly solvable
in the large N limit. We study the general renormalizable N=1 U(N)
Chern-Simons gauge theory coupled to a single massive fundamental matter
multiplet. At leading order in the 't Hooft large N limit we present
computations and conjectures for the 2×2 S matrix in these
theories. Our results apply at all orders in the 't Hooft coupling and the
matter self interaction. The S matrices are in perfect agreement with the
recently conjectured strong-weak coupling self duality of this class of
theories. The consistency of our results with unitarity requires a delta
function at forward scattering and modification of the usual rules of
crossing symmetry in precisely the manner as anticipated in
arXiv:1404.6373, lending substantial support to the conjectures of that
paper. In a certain range of coupling constants the bosonic and fermionic
S matrices have a pole whose mass vanishes on a self dual codimension one
surface in the space of couplings suggesting the existence of a gapless
decoupled sector in the theory.
References: arxiv:1505.06571, arxiv:1404.6373 (click to hide)
Fri
27.11.
11:00
Bern
Keller, Penedones, Sonner
GeNeZiSS: “3 talks”
abstract (click to view) Venue: Room 331, Main Building, Bern University
Schedule:
11.00 -- 11.30: Coffee/Tea Welcome
11.30 -- 12.30: Speaker 1
12.30 -- 14.00: Lunch Break
14.00 -- 15.00: Speaker 2
15.00 -- 15.30: Coffee/Tea Break
15.30 -- 16.30: Christoph Keller (click to hide)
Wed
02.12.
11:30
HIT E41.1
Pan Kessel (AEI Potsdam)
“Higher spins coupled to scalars”
abstract (click to view) This talk has two parts. In the first one I will try to explain what three dimensional Vasiliev theory is good for and discuss some recent results obtained from it. In this part I will not dive into the technical details of Vasiliev theory but focus on its physical implications. In the second part I will sketch how Vasiliev theory works in a (hopefully) pedagogical manner. (click to hide)
Wed
09.12.
11:30
HIT E41.1
Yunfeng Jiang (ETH Zürich)
“Three-point functions in N=4 Super-Yang-Mills theory from integrability”
abstract (click to view) It is widely accepted that N=4 Super-Yang-Mills theory is integrable in
the planar limit. In this talk, I will review the developments in computing
three-point functions using the powerful tools of integrable systems in the
past five years. I will explain the basic ideas and then discuss several
interesting cases and their relations to other domains of mathematical
physics. (click to hide)
Wed
16.12.
11:30
HIT E41.1
Louise Anderson (Imperial College London)
“Mass-deformations and quantum phase transitions”
abstract (click to view) I will briefly review how the technique of localisation may be used to compute exact quantities in supersymmetric gauge theories. This allows for non-trivial tests of the AdS/CFT-correspondence, but it also gives us an opportunity to obtain more information about the gauge theories themselves. I will focus on mass-deformed theories in the so-called decompactification limit, where they have been shown to have a very rich phase structure, and I will consider an analytically continued version of ABJM theory as an explicit example. When the theory is deformed by a large mass, an infinite serie of quantum phase transitions are found as we move from weak to strong coupling, accumulating in the strong coupling limit. Under such conditions, this kind of phase transitions should also be visible in the dual gravity theory. (click to hide)

last modified: Thu, 17 Dec 2015, 09:19 CET

Spring Semester 2016

Wednesday, 14:00, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel and Christoph Keller

day
date
time
venue
speaker
title
Wed
17.02.
14:00
HIT E41.1
Simon Badger (CERN)
“Integrand representations of two-loop five point amplitudes in QCD”
abstract (click to view) I will discuss recent progress towards the computation of two-loop scattering amplitudes contributing to three jet production at NNLO. Imposing on-shell symmetry constraints to the amplitudes can lead to compact forms of amplitudes and integrands. I will discuss two explicit examples of this, colour-kinematics relations and manifest infra-red behaviour via local integrands, and show how they can be incorporated within integrand reduction methods (click to hide)
Mon
22.02.
16:45
HIT H42
Marcio Martins (Universidade Federal de São Carlos)
Theoretical Physics Colloquium: “Lattice Gas Automaton and Super Spin Chains”
abstract (click to view) The scaling of the trajectories of particles moving through obstacles randomly placed on a lattice can be captured by the critical exponents of spin chains. For simple scattering rules allowing crossing of the paths there is a mapping to an integrable spin chain invariant by the orthosympletic superalgebra. The size distribution of the trajectories scale with logarithmic corrections and this is associated to the existence of a continua of scaling dimensions on top of the spin chain ground state. (click to hide)
Wed
02.03.
14:00
HIT E41.1
Stijn van Tongeren (HU Berlin)
“Quantum deformations and Wick rotations”
abstract (click to view) Many integrable deformations of the AdS₅×S5 string have been investigated in recent years. Out of these, the one that corresponds to a quantum deformation at the algebraic level, appears to be the most difficult to interpret. Motivated by this I will discuss quantum deformations of the flat space string instead. In addition to its link to the AdS₅×S⁵ string by a Wigner-İnönü contraction, surprisingly this deformed flat space string is related to the AdS₅×S⁵ string by a double Wick rotation in a light cone gauge, at least bosonically. This gives insight into the symmetries of the so-called mirror model underlying finite size (coupling) integrability in AdS/CFT. Moreover, as this model is T dual to a type IIB* string on dS₅×H⁵, this indicates interesting relations between symmetry algebras under T duality. At the fermionic level there is slight tension in this story with regard to the contraction of the quantum deformed AdS₅×S⁵ string, but I will argue that this might in fact be taken as motivation to reexamine the latter. (click to hide)
Wed
09.03.
14:00
HIT E41.1
Subhajit Mazumdar (TIFR Mumbai)
“A Membrane Paradigm : The Next to Leading Order Story”
abstract (click to view) It has recently been demonstrated that black hole dynamics can be reformulated as the equations of motion of a codimension one membrane (roughly the black hole event horizon). These membrane equations have previously been determined at leading order in the large D expansion. In this talk we implement this `duality' to next order in 1/D and thereby determine the leading corrections to the membrane equations of motion. Our results obey several consistency checks; in particular upon linearizing our equations about a spherical membrane we reproduce the known quasinormal mode frequencies of large D Schwarschild black holes, including first subleading corrections in 1/D. (click to hide)
Wed
16.03.
11:30
HIT E41.1
Cindy Keeler (Niels Bohr Institute)
“Partition Functions in Even Dimensional AdS via Quasinormal Mode Methods”
Wed
16.03.
14:00
HIT E41.1
Tom Rudelius (Harvard)
“The Weak Gravity Conjecture: Variants and Inflationary Implications”
Wed
23.03.
14:00
HIT E41.1
Johannes Brödel (HU Berlin)
“Elliptic multiple zeta values and a special derivation algebra”
abstract (click to view) While usual multiple zeta values carry the transcendentality in many results of calculations in quantum field theory as well as tree-level string theory, elliptic multiple zeta values take this role in several higher-loop calculations and – most prominently – in one-loop open-string amplitudes.
After a short review of multiple zeta values, I will introduce and describe their elliptic analogues. While discussing their appearance, properties and relations, I will explain the connection to iterated Eisenstein integrals and a special derivation algebra, which in turn allows to predict the number of indecomposable elements at given weight and length, thus leading to canonical representations of the results. (click to hide)
Wed
30.03.
14:00
HIT E41.1
Zoltan Bajnok (Wigner Research Center for Physics, Budapest)
“String field theory vertex, 3pt functions and form factors”
abstract (click to view) The bootstrap program aims to solve integrable models completely by determining the scattering matrix of the particles and the form factors of local operators. These infinite volume quantities then can be used to build the full spectrum and correlation functions at any finite size.
In the talk I will explain the adaptation of the form factor bootstrap program to calculate the 3pt functions of N=4 SYM theory and the lightcone string field theory vertex of AdS₅×S⁵. The HHL 3pt functions will be mapped to diagonal form factors of local operators, while the SFT vertex to the form factors of a nonlocal operator. I will also show the relation of our ideas to the hexagon approach of Basso, Komatsu and Vieira. (click to hide)
Wed
13.04.
14:00
HIT E41.1
Benjamin Basso (ENS Paris)
“Hexagons and Three-Point Functions”
abstract (click to view) I will present a framework for computing correlators of three single trace operators in planar N=4 SYM theory that uses hexagonal patches as building blocks. This approach allows one to exploit the integrability of the theory and derive all loop predictions for its structure constants. After presenting the main ideas and results, I will discuss recent perturbative tests and open problems. (click to hide)
Wed
20.04.
14:00
HIT E41.1
Mikael von Strauss (Institut d’Astrophysique de Paris)
“Partial masslessness beyond de Sitter”
abstract (click to view) It is known that the de Sitter group admits so called short representations for massive spin-2 fields when the mass and cosmological constant saturate the Higuchi bound. In the linear theory of a massive spin-2 field propagating on Einstein spacetimes this is manifested via the emergence of a new linear gauge symmetry when the Higuchi bound is saturated. As a result of this gauge symmetry the helicity-0 mode of the massive spin-2 decouples and the theory only propagates 4 helicity modes (±2, ±1), a phenomenon which is known as partial masslessness. A long outstanding problem is whether this can be extended to a fully non-linear symmetry, or equivalently whether the phenomena of partial masslessness extends beyond Einstein spacetimes to completely general spacetimes. In this talk I will give an overview of the problem and discuss why it is an important problem to resolve and also present some recent developments in this pursuit. The general analysis is quite involved and is still an open problem, but I will demonstrate a restricted class of non-Einstein spacetimes which do indeed propagate a partially massless spin-2 field. (click to hide)
Wed
27.04.
14:00
HIT E41.1
Bo Sundborg (Stockholm University)
“The sky is the limit: free boundary conditions in AdS₃ Chern-Simons theory”
Mon
02.05.
16:45
HPV G4
Ashoke Sen (HRI Allahabad)
Schroedinger Lecture: “Ultraviolet and infrared divergences in string theory”
Tue
03.05.
11:30
HIT K51
Ashoke Sen (HRI Allahabad)
Special Course: “Aspects of Superstring Perturbation Theory I”
Wed
04.05.
14:00
HIT E41.1
Thomas Dumitrescu (Harvard)
“Current Algebra Constraints on BPS Particles”
Tue
10.05.
11:30
HIT K51
Ashoke Sen (HRI Allahabad)
Special Course: “Aspects of Superstring Perturbation Theory II”
Tue
10.05.
14:00
HIT K51
Ashoke Sen (HRI Allahabad)
Special Course: “Aspects of Superstring Perturbation Theory III”
Wed
18.05.
14:00
HIT E41.1
Sasha Zhiboedov (Harvard)
“The S-matrix Bootstrap and The Leading Regge Trajectory”
abstract (click to view) We consider a tree-level meromorphic, unitary and crossing
symmetric scattering amplitude. We set up bootstrap equations and
use them together with unitarity to constrain the asymptotic form
of the leading Regge trajectory. (click to hide)
Wed
25.05.
14:00
HIT E41.1
Yvonne Geyer (University of Oxford)
“Loop Integrands from the Riemann sphere”
abstract (click to view) Worldsheet formulations of quantum field theories have had wide ranging
impact on the study of scattering amplitudes. However, the mathematical
framework becomes very challenging on the higher-genus worldsheets required
to describe loop effects. After a general introduction, I will describe how
in such worldsheet models based on the scattering equations, formulae on
higher-genus surfaces can be transformed to remarkably simple expressions
on the Riemann sphere. (click to hide)
Wed
01.06.
14:00
HIT E41.1
Ben Hoare (ETH Zürich)
“Yang-Baxter deformations and superstrings”
abstract (click to view) Our understanding of Yang-Baxter deformations of the AdS₅×S⁵ superstring has improved a great deal over the past year. However, a definite answer to one question remains elusive. Are the deformations themselves superstring theories? In this talk I will introduce the deformed models and highlight various features using simple examples. In the second half I will discuss their current status as superstring theories or otherwise. (click to hide)
Wed
13.07.
11:30
HIT E41.1
Nima Khosravi (Shahid Beheshti U.)
“Ensemble Average Theory of Gravity”
abstract (click to view) We put forward the idea that all the theoretically consistent models of gravity have contributions to the observed gravity interaction. In this formulation, each model comes with its own Euclidean path-integral weight where general relativity (GR) has automatically the maximum weight in high-curvature regions. We employ this idea in the framework of Lovelock models and show that in four dimensions the result is a specific form of the f(R,G) model. This specific f(R,G) satisfies the stability conditions and possesses self-accelerating solutions. Our model is consistent with the local tests of gravity since its behavior is the same as in GR for the high-curvature regime. In the low-curvature regime the gravitational force is weaker than in GR, which can be interpreted as the existence of a repulsive fifth force for very large scales. Interestingly, there is an intermediate-curvature regime where the gravitational force is stronger in our model compared to GR. The different behavior of our model in comparison with GR in both low- and intermediate-curvature regimes makes it observationally distinguishable from ΛCDM. (click to hide)

last modified: Thu, 7 Jul 2016, 17:26 CEST

Fall Semester 2016

Tuesday, 11:30, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel and Christoph Keller

day
date
time
venue
speaker
title
Tue
20.09.
11:30
HIT E41.1
Balt van Rees (Durham University)
“The S-matrix bootstrap revisited”
abstract (click to view) We take a fresh look at the S-matrix bootstrap program using modern tools inspired by the revived conformal bootstrap. There exist various approaches to taming the landscape of S-matrices. We will discuss two different methods and show that they both lead to the same universal bound for the interaction strength in 2-dimensional QFTs. We propose a specific numerical algorithm for higher-dimensional QFTs and present some initial results. (click to hide)
Tue
11.10.
11:30
HIT E41.1
Tomas Prochazka (LMU Munich)
“W-symmetry, topological vertex and affine Yangian”
Tue
25.10.
11:30
HIT E41.1
Carlo Meneghelli (SUNY Stony Brook)
“Pre-fundamental representations for the Hubbard model and AdS/CFT”
Tue
01.11.
11:30
HIT E41.1
Mahdi Godazgar (ETH Zurich)
“The first law of entanglement entropy and the Sparling form”
Thu
03.11.
15:15
HG G43
Boris Pioline (CERN)
Talks in mathematical physics: “Indefinite theta series and generalized error functions”
Tue
08.11.
11:30
HIT E41.1
Alexandre Belin (University of Amsterdam)
“Universality of Sparse d>2 Conformal Field Theory at Large N”
Tue
15.11.
11:30
HIT E41.1
Ida Zadeh (ETH Zurich)
“Operator mixing in the D1-D5 CFT”
Tue
22.11.
11:30
HIT E41.1
Sylvain Ribault (CEA Saclay)
“A conformal bootstrap approach to the Potts model”
abstract (click to view) We study four-point functions of the Potts model, with two-dimensional critical percolation as a special case. We propose an exact ansatz for the spectrum: an infinite, discrete and non-diagonal combination of representations of the Virasoro algebra. Based on this ansatz, we compute four-point functions using a numerical conformal bootstrap approach. The results agree with Monte-Carlo computations of connectivities of random clusters.
If time allows we will discuss the interpretation of our results in terms of a conformal field theory that might be related to non-diagonal minimal models and to Liouville theory. (click to hide)
Tue
29.11.
11:30
HIT K51
Livia Ferro (LMU Munich)
“The amplituhedron for tree-level scattering amplitudes in N=4 sYM”
abstract (click to view) In this talk I will present work in progress on the amplituhedron formulation of scattering amplitudes. Recently it has been conjectured that amplitudes in planar N=4 sYM are nothing else but the volume of a completely new mathematical object, called amplituhedron, which generalises the positive Grassmannian. After a review of the main ingredients which will be used, I will discuss some of the questions which remain open in this framework. I will then describe a new direction which promises to solve these issues and compute the volume of the amplituhedron at tree level. (click to hide)
Thu
01.12.
15:15
HG G43
David Hernandez (Université Paris-Diderot)
Talks in mathematical physics: “Spectra of quantum KdV Hamiltonians, Langlands duality and category O for quantum affine algebras”
Tue
06.12.
11:30
HIT E41.1
Blagoje Oblak (ETH Zurich)
“Wigner Rotations for BMS Particles”
abstract (click to view) This talk is devoted to irreducible unitary representations of the BMS group in three dimensions, which physically correspond to standard particles dressed with quantized boundary gravitons. After reviewing their classification in terms of coadjoint orbits of the Virasoro group, I will turn to spinning particles and show how one can compute the corresponding "Wigner rotations", whose experimental signature should be a BMS analogue of Thomas precession. (click to hide)
Tue
13.12.
11:30
HIT K52
Erik Tonni (SISSA)
“Entanglement hamiltonians in 2D CFT and Shape dependence of holographic entanglement entropy in AdS₄/CFT₃”
abstract (click to view) In the first part we enumerate the cases in 2d conformal field theory where the logarithm of the reduced density matrix (the entanglement hamiltonian) may be written as an integral over the energy-momentum tensor times a local weight. These include some known time-independent cases and also new examples corresponding to the time-dependent scenarios of a global and local quench.
In the second part we discuss the holographic entanglement entropy in AdS₄/CFT₃ for finite domains with generic shapes. For smooth shapes the constant term can be evaluated by employing a generalisation of the Willmore functional for two dimensional surfaces. Explicit examples are given for asymptotically AdS₄ black holes and domain wall geometries.
The latter geometries allow to explore the behaviour of the holographic entanglement entropy under RG flows. (click to hide)
Tue
20.12.
11:30
HIT E41.1
Alessandro Torrielli (University of Surrey)
“Integrability and massless modes in the AdS3/CFT2 correspondence”
abstract (click to view) We will discuss massless modes in the integrable system underlying the AdS3/CFT2 correspondence. In the first part, we will discuss the general expectations from the classic analysis of integrable massless scattering. In the second part, we will introduce a q-Poincaré superalgebra which turns out to be an additional symmetry of the massless sector, and in particular we will display how the action of boosts is realised. In the third part, we will show the equation which the massless S-matrix satisfies and which is interpreted as its boost invariance, and how this might lead to an emergent geometric reformulation of the problem. (click to hide)
Tue
17.01.
11:30
HIT E41.1
David Marsh (University of Cambridge)
“Manyfield inflation”
abstract (click to view) The primordial perturbations inferred from observations of the Cosmic Microwave Background and the large-scale structure of the universe are quite simple: they are to a good approximation Gaussian, approximately scale-invariant and consistent with some of the simplest models of single-field slow-roll inflation. In this talk I will review the theoretical and observational motivations for going beyond the single-field description, and I will describe the significant challenges in studying models of inflation with several interacting fields. I will discuss a new method for studying classes of models of multifield inflation utilising on a non-equilibrium description of random matrix theory (Dyson’s Brownian Motion). This method makes it for the first time possible to study inflation in systems with a large number of interacting fields, and I will discuss the observational predictions of manyfield inflation. Strikingly, as the number of interacting fields (and hence the complexity of the model) increases, the power spectra of curvature perturbations simplify, and become more predictive. I will explain how these results can be understood in terms of universal properties of large, random matrices. (click to hide)

last modified: Wed, 11 Jan 2017, 10:23 CET

Spring Semester 2017

Wednesday, 14:00, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel, Mahdi Godazgar, Christoph Keller and Blagoje Oblak

day
date
time
venue
speaker
title
Thu
23.02.
15:15
HG G43
Wellington Galleas (ETH Zürich)
Talks in Mathematical Physics: “Partition function of the elliptic gl₂ SoS model as a single determinant”
abstract (click to view) Partition functions of vertex models with domain-wall boundaries have appeared in a variety of contexts ranging from enumerative combinatorics to the study of gauge theories. The six-vertex model is the prototype model where such boundary conditions were adopted and, in that case, the model's partition function admits a compact representation in terms of a single determinant. Such representation has led to a number of developments in the field but seemed to be restricted to the six-vertex model. The next natural candidate for this study is the elliptic gl₂ Solid-on-Solid (SoS) model but, despite all efforts, the results suggested single determinantal representations did not exist. This problem has only been recently solved with the help of special functional equations originating from the dynamical version of the Yang-Baxter algebra. In this talk I will discuss this problem and show how families of single determinantal representations for the elliptic SoS model's partition function can be derived in a constructive manner. (click to hide)
Wed
01.03.
14:00
HIT J 53
Monica Guica (CEA Saclay)
“Towards a background-independent construction of the bulk field in AdS₃”
Wed
08.03.
14:00
HIT E41.1
Pietro Longhi (Uppsala university)
“Wall crossing invariants from spectral networks”
abstract (click to view) In presence of defects the Hilbert space of a quantum field theory can change in interesting ways. Surface defects in 4d N=2 theories introduce a class of 2d-4d BPS states, which the original 4d theory does not possess. For theories of class S, spectral networks count 2d-4d BPS states, and through the 2d-4d wall-crossing phenomenon the 4d BPS spectrum can be obtained. Adopting this physical viewpoint on spectral networks, I will illustrate some recent and ongoing developments based on this framework, with applications to the study of 4d N=2 BPS monodromies and their relations to specialisations of the superconformal index. (click to hide)
Wed
15.03.
14:00
HIT E41.1
Jens Hoppe (KTH Stockholm)
“Quantized Minimal Surfaces”
abstract (click to view) Concerns solutions of the equation [Xₖ,[Xₖ,Xₘ]]=0 (click to hide)
Wed
22.03.
14:00
HIT E41.1
Jacob Bourjaily (Niels Bohr Institute)
“Stratifying On-Shell Cluster Varieties”
abstract (click to view) There exists a deep correspondence between a class of physically important functions—called "on-shell functions"—and certain (cluster variety) subspaces of Grassmannian manifolds, endowed with a volume form that is left invariant under cluster coordinate transformations. These are called "on-shell varieties" (which may or may not include all cluster varieties). It is easy to prove that the number of on-shell varieties is finite, from which it follows that the same is true for on-shell functions. This is powerful and surprising for physics, because these on-shell functions encode complete information about perturbative quantum field theory.
In this talk, I describe the details of this correspondence and how it is constructed and give the broad physics motivations for obtaining a more systematic understanding of on-shell cluster varieties. I outline a general, brute-force strategy for classifying these spaces; and describe the results found by applying this strategy to the case of Gr(3,6). (click to hide)
Wed
29.03.
14:00
HIT E41.1
Marc Magro (ENS Lyon)
“The twist function of an integrable sigma-model”
abstract (click to view) I shall review the relevance of the twist function for a whole family of integrable sigma-models. In particular, I will show how this function is related to the computation of both local and non-local conserved charges. (click to hide)
Wed
05.04.
14:00
HIT E41.1
Ali Seraj (IPM Tehran)
“Multipole charges in electrodynamics and the vacuum moduli space”
abstract (click to view) We introduce multipole charges as the Noether charges associated with a subclass of gauge symmetries of Maxwell theory. We show that in a static configuration, these charges are proportional to the electric multipole moments which uniquely specify the system. Moreover, the conservation laws impose infinite number of constraints over the radiation in electrodynamics. The presence of multipole symmetries implies that the vacuum of gauge theory is not unique, but instead an infinite dimensional moduli space, the adiabatic motion on which generates well known solutions of the theory. (click to hide)
Wed
12.04.
14:00
HIT E41.1
James Bonifacio (University of Oxford)
“Constructing and constraining massive spin-2 scattering amplitudes”
abstract (click to view) I will first review a procedure for constructing tree-level scattering amplitudes for spinning particles. Considering the case of a self-interacting massive spin-2 particle, I show that the four-point amplitudes with the highest cutoff correspond to the known ghost-free massive gravity theories, even allowing for arbitrary derivative interactions and parity-odd terms. This demonstrates that $\Lambda_3$ is a model-independent bound on the strong coupling scale in effective theories of a self-interacting massive spin-2 field. I also remark on possible generalisations to higher spins and additional fields. Lastly, I will discuss how the scattering amplitudes of massive spin-2 theories are constrained by analytic dispersion relations, assuming the existence of a UV-completion that satisfies the usual S-matrix analyticity conditions. (click to hide)
Wed
26.04.
14:00
HIT E41.1
Hjalmar Rosengren (Chalmers university)
“Combinatorics of elliptic lattice models”
Wed
03.05.
14:00
HIT E41.1
Michal Heller (AEI, Potsdam)
“Towards complexity for QFT states: a cMERA study”
Wed
10.05.
14:00
HIT E41.1
Petr Horava (UC Berkeley)
“Nonrelativistic Naturalness, Aristotelian Spacetime and the Higgs Mass Hierarchy”
Wed
24.05.
14:00
HIT E41.1
Prem Kumar (University of Swansea)
“Scrambling time and Lyapunov exponent for higher spin perturbations”
Wed
31.05.
14:00
HIT K51
Elli Pomoni (DESY)
“2D CFT for class Sk theories”
Wed
14.06.
14:00
HIT E41.1
Didina Serban (CEA Saclay)
“Correlation functions from integrability”
abstract (click to view) The talk will review the computation of the three point function of gauge-invariant operators in the
planar N=4 SYM theory using integrability-based methods.
The structure constant can be decomposed, as proposed by Basso, Komatsu and Vieira, in terms of two hexagons, which can be understood as form factors of twist fields introducing a curvature defect. One of the main challenges in this approach is to perform the sum over virtual particles emitted and absorbed by the hexagons in different channels. I will discuss a method to perform these sums, the contributions currently accessible, the comparison with the results obtained by semiclassics. (click to hide)

last modified: Fri, 14 Jul 2017, 14:55 CEST

Fall Semester 2017

Tuesday, 11:30, HIT E41.1

Organised by: Niklas Beisert, Mahdi Godazgar, Christoph Keller and Blagoje Oblak

day
date
time
venue
speaker
title
Tue
19.09.
11:30
HIT E41.1
Benoit Vicedo (University of Hertfordshire)
“Integrable field theories and dihedral affine Gaudin models”
abstract (click to view) The quantisation of so called non-ultralocal classical integrable field theories is an important open problem in Mathematical Physics. I will explain how this problem can be reformulated mathematically within the framework of affine Gaudin models. I will also motivate this new perspective on non-ultralocality as a way of understanding the massive ODE/IM correspondence, a conjectural classical/quantum duality in integrable field theories. (click to hide)
Tue
03.10.
11:30
HIT E41.1
Sameer Murthy (King's College, London)
“Entanglement, Replicas, and Thetas”
Tue
03.10.
13:30
ETH-ITS
Johannes Noller (ETH ITS)
ITS Fellows' Seminar: “The universe's toolkit: What gravity is fundamentally made of”
abstract (click to view) In this talk I will give a whistle-stop tour of our current understanding of the fundamental building blocks of gravity in close analogy to the way in which we understand the other forces in nature. I will show to what extent we have already decoded nature's blueprint at this level, where recent progress has been made and how all this affects observable phenomena from the very large (e.g. the evolution of galaxies) to the very small (e.g. the discovery of new elementary particles). Along the way I will also highlight where some long-standing challenges to our current best theories of gravity exist and how recent theoretical progress may assist in resolving them. (click to hide)
Tue
10.10.
11:30
HIT E41.1
Linus Wulff (Masaryk University)
“Classifying integrable symmetric space strings”
abstract (click to view) We show how the requirement of factorized scattering can be used to rule out integrability for strings in AdS backgrounds. This leads to a classification in the case of symmetric spaces. (click to hide)
Tue
17.10.
11:30
HIT E41.1
Charles Melby-Thompson (Julius-Maximilians-Universität Würzburg)
“Double Trace Defects in Holography”
abstract (click to view) Perhaps the simplest RG flows in the AdS/CFT correspondence are those triggered by double trace deformations, which are realized holographically by a choice of boundary asymptotics for the fluctuations of a scalar field in the unitarity window. We consider the holographic realization of RG interfaces separating the two ends of this RG flow, which we call double trace interfaces.
In the limit of large central charge, we derive the spectrum of non-trivial interface operators, the 2-point function, and relations between the bulk and interface OPE coefficients. We show that our results match conformal perturbation theory in the regime where both methods are valid. We also compute the interface g-factor.
We further argue that within 3d higher spin gravity, our construction realizes the integrable RG defects in the W_{N,k} minimal models studied by Gaiotto. We reproduce the large-N limit of several of Gaiotto’s overlap coefficients and, computing the interface g-factor exactly in CFT, find that at large N it coincides with our holographic result. (click to hide)
Tue
24.10.
11:30
HIT E41.1
Andrea Campoleoni (ETH Zürich)
“Higher-spin BMS symmetries in four dimensions and soft theorems”
Tue
31.10.
11:30
HIT E41.1
Hagen Muenkler (ETH Zürich)
“Symmetries of smooth Wilson loops”
Tue
07.11.
11:30
HIT E41.1
Sergey Frolov (Trinity College, Dublin)
“Free field representation of the Zamolodchikov-Faddeev algebra and form factors of the SU(N) x SU(N) Principal Chiral Field model”
abstract (click to view) A free field representation of the Zamolodchikov-Faddeev algebra of the SU(N) x SU(N) Principal Chiral Field model is constructed, and used to derive an integral representation for form factors of a multi-parameter family of exponential fields. (click to hide)
Tue
07.11.
14:00
HIT E41.1
Vasily Pestun (IHES)
“Non-simply laced q-deformed W-algebras from fractional instantons”
abstract (click to view) I will discuss the construction of the generators of q-deformed W-algebra(g) for arbitrary simple Lie algebra g, including the non-simply laced cases, in terms of the geometry of the moduli spaces of fractional instantons and Coulomb branches of fractional quiver gauge theories. (click to hide)
Tue
14.11.
11:30
HIT E41.1
Jules Lamers (Chalmers University)
“Resurrecting the q-analogue of the Haldane–Shastry spin chain”
Tue
21.11.
11:30
HIT K52
Florian Loebbert (Humboldt University)
“Yangian Symmetry for Fishnet Feynman Graphs”
Tue
05.12.
11:30
HIT E41.1
Edoardo Vescovi (U. Sao Paulo)
“Two non-BPS Wilson loops: quark-antiquark potential in defect CFT and circular loop beyond the wavy approximation”
abstract (click to view) I will describe interesting features of two observables measured by non-BPS Wilson loops.
In the first part I determine the potential energy of a quark-antiquark pair in a Higgsed variant of N=4 SYM with a codimension-1 defect [1708.04884] at weak coupling via gauge perturbation theory and at strong coupling in the dual D3-D5 brane system. In the latter regime, the relevant string free energy displays Gross-Ooguri transitions between a connected string surface and a phase where the string breaks into two disconnected surfaces.
In the second part I consider small deformations of the circular Wilson loop in N=4 SYM and of the dual minimal surface in hyperbolic space H_3. The formalism introduced by Kruczenski showed that the Wilson loop vev at strong coupling is invariant under certain deformations of the boundary contour. This symmetry was later found by Dekel to break down at weak coupling only at an unexpected high order in the deformation parameter. I report ongoing progress to understand this approximate symmetry in gauge theory. (click to hide)
Tue
12.12.
11:30
HIT E41.1
Joan Simon (University of Edinburgh)
“EPR=ER in LLM”

last modified: Wed, 6 Dec 2017, 14:27 CET

Spring Semester 2018

Tuesday, 14:00, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel, Mahdi Godazgar and Blagoje Oblak

day
date
time
venue
speaker
title
Wed
31.01.
11:30
HIT E41.1
Pujian Mao (Chinese Academy of Sciences, Beijing)
“The triangle relation and beyond”
abstract (click to view) Soft theorems, memory effects, and asymptotic symmetries have been shown in recent years to be mathematically equivalent. In this talk, I will give an overview of this fascinating triangle equivalence. In particular, I will explain in detail a very recent prescription to realize this triangle relation beyond the leading order. (click to hide)
Tue
20.02.
14:00
HIT E41.1
Shota Komatsu (IAS Princeton)
“Exact Correlators on the BPS Wilson Loops”
Tue
27.02.
14:00
HIT E41.1
Nicolas Boulanger (University of Mons)
“Uniqueness of N=2 and 3 pure supergravities in 4D”
Wed
28.02.
09:30
HIT E41.1
Arkady Tseytlin (Imperial College, London)
“Non-supersymmetric Wilson loop in N=4 SYM and 1d CFT”
Tue
06.03.
14:00
HIT E41.1
Max Riegler (ULB)
“Warped Black Holes in Lower Spin Gravity”
abstract (click to view) In this talk I present a novel and very efficient description of space-like warped Anti-de Sitter black holes in terms of a lower-spin Chern-Simons theory. I will explain in detail how to treat the thermodynamics of these black holes in the Chern-Simons formulation and what initial assumptions have to be made. In the rest of the talk I will take great care to explain why these initial assumptions are reasonable using various arguments such as: arguments based on warped conformal field theories, holographic entanglement entropy and a metric interpretation of the Chern-Simons results. I will also mention how these results can be used for possible higher-spin extensions of space-like warped higher-spin black holes. (click to hide)
Tue
13.03.
14:00
HIT E41.1
Julian Sonner (University of Geneva)
“Black Holes as Pure States”
Tue
20.03.
14:00
HIT E41.1
Kirill Krasnov (University of Nottingham)
“Colour/kinematics duality in YM and the Drinfeld double of the Lie algebra of diffeomorphisms”
Tue
27.03.
14:00
HIT E41.1
Konstantin Zarembo (Nordita)
“String quantum corrections to holographic Wilson loops”
abstract (click to view) Minimal area law, that holds for Wilson loops at strictly infinite coupling, has been extensively checked using localization and integrability. Computing quantum corrections to the area law at the same time is riddled with puzzles. I will concentrate on the ratio of Wilson loops that share the same contour on the boundary but have different coupling to scalars. A mismatch between field theory and holography has been reported for a ratio of this type. I will show that an IR anomaly associated with the singular conformal gauge has to be taken into account to reconcile the string calculation with the known field theory result for the Wilson loops. (click to hide)
Wed
28.03.
14:00
HIT E41.1
Till Bargheer (Uni Hannover)
“Handling Handles -- Non-Planar AdS/CFT Integrability”
abstract (click to view) I will explain how non-planar corrections to correlation functions in
N=4 super Yang-Mills theory can be computed via the recently developed
integrability-based method of hexagonalization.
Reference: https://arxiv.org/abs/1711.05326 (click to hide)
Tue
24.04.
14:00
HIT E41.1
Amit Sever (Tel Aviv University)
“Non-planar Scattering amplitudes in N=4 SYM theory”
abstract (click to view) I'll discuss the paper 1802.09395 where we study the first non-planar correction to gluon scattering amplitudes in N=4 SYM theory. The correction takes the form of a double trace partial amplitude and is suppressed by one power of 1/N with respect to the leading single trace contribution. We extend the duality between planar scattering amplitudes and null polygonal Wilson loops to the double trace amplitude. The new duality relates the amplitude to the correlation function of two infinite null polygonal Wilson lines that are subject to a quantum periodicity constraint. We test the duality perturbatively at one-loop order and demonstrate it for the dual string in AdS. The duality allows us to extend the notion of the loop integrand beyond the planar limit and to determine it using recursion relations. It also allows us to apply the integrability-based pentagon operator product expansion approach to the first non-planar order. (click to hide)
Tue
08.05.
14:00
HIT E41.1
Sara Pasquetti (Milano Bicocca)
“T[SU(N)] duality webs”
abstract (click to view) I will discuss various new IR dualities between 3d N=2 quiver theories. Some of the 3d theories that I will discuss can be interpreted as codimension-two defect theories coupled to a 5d bulk theory, in this case the 3d duality follows from a duality for the bulk theory. Finally I will discuss the gauge/q-CFT correspondence relating pairs of 3d dual theories to spectral dual correlators of q-deformed Toda vertex operators and discuss the reduction from 3d to 2d. (click to hide)
Wed
16.05.
11:00
HIT E41.1
Roberto Volpato (INFN Padova)
“A Borcherds-Kac-Moody superalgebra with Conway symmetry”
Tue
29.05.
14:00
HIT E41.1
Yacine Ikhlef (Université Pierre et Marie Curie)
“Entanglement entropies of minimal models from null-vector equations”
abstract (click to view) We present a new method to compute Rényi entropies in one-dimensional critical systems. The null-vector conditions on the twist fields in the cyclic orbifold allow us to derive a differential equation for their correlation functions. The latter are then determined by standard bootstrap techniques. We apply this method to the calculation of various Rényi entropies in the non-unitary Yang-Lee model.
Joint work with B. Estienne and Th. Dupic (click to hide)

last modified: Thu, 20 Dec 2018, 15:02 CET

Fall Semester 2018

Wednesday, 11:00, HIT E41.1

Organised by: Matthias Gaberdiel, Blagoje Oblak, Hagen Münkler

day
date
time
venue
speaker
title
Thu
16.08.
11:00
HIT E41.1
Kiryl Pakrouski (Princeton)
“Spectrum of O(4)^3 Majorana Tensor Model: SYK-like system without disorder”
Tue
25.09.
11:30
HIT E41.1
Agnese Bissi (Uppsala University)
“Analytic conformal boostrap and its applications”
Wed
03.10.
11:00
HIT E41.1
Piotr Tourkine (CERN)
“New twisted string theories”
abstract (click to view) Twistor strings have undergone a renewal of interest since the discovery of the Cachazo-He-Yuan formalism for scattering amplitudes in field theory in 2013. These formulae deeply challenge the way we think about scattering amplitudes in quantum field theory and are neatly explained by the so-called ambitwistor string, a cousin of the old twistor string. The existence of these remarkable formalisms, which I shall present to you during the talk, called for a connection to good old string theory. The answer to this question is now understood: it relies on counter-intuitive limits and crucially, the existence of a different quantization for string theory, which we called “twisted strings”. The first part of the talk will be concerned on making that connection to string theory clear. In the second part of the talk, I’ll report on recent results obtained with Eduardo Casali on the winding modes of these twisted strings. They give rise to new exotic target space theories, naively non unitary, but exhibiting features half way between string and field theory. In particular, they are T-duality symmetric. (click to hide)
Wed
10.10.
11:00
HIT E41.1
Rob Klabbers (Humboldt University)
“Holographic correlators finally cracked”
abstract (click to view) In this talk I will discuss recent advances in the computation of four-point functions of 1/2 BPS operators in N=4 SYM using AdS/CFT. These are the simplest dynamical correlation functions and their study goes back to the early days of AdS/CFT research. Not long ago the proposition of a closed formula in Mellin space for the strong-coupling limit of these four-point functions rekindled interest in them, as further results could disprove or corroborate the conjectured formula. I will discuss how one can compute the strong-coupling limit of these correlation functions using the supergravity action through the AdS/CFT correspondence. I will in particular explain how the algorithm was recently improved to allow for the computation of virtually any correlator of 1/2 BPS operators. Moreover, I will explain how to go from these coordinate space results to Mellin space and back. (click to hide)
Wed
17.10.
11:00
HIT E41.1
Pietro Longhi (ETH Zurich)
“BPS counting in five dimensions with lagrangian defects”
Wed
24.10.
11:00
HIT E41.1
Ruben Monten (CEA Saclay)
“Higher spin quantum gravity in de Sitter space”
Wed
31.10.
11:00
HIT E41.1
Roberto Tateo (INFN Turin)
“TTbar-deformed classical and quantum field theories”
abstract (click to view) Surprising links between the deformation of 2D quantum field theories induced by the composite $T \bar{T}$ operator, effective string models and the AdS/CFT correspondence, have recently emerged. I will discuss various classical and quantum aspects of this special irrelevant perturbation, including its geometrical interpretation at classical level. (click to hide)
Wed
07.11.
11:00
HIT E41.1
Ben Gripaios (University of Cambridge)
“Topological Actions and Differential Cohomology”
Wed
14.11.
11:00
HIT E41.1
Enrico Brehm (AEI Golm)
“Universal results on matrix elements in CFT from modular covariance”
Tue
20.11.
11:30
HIT E41.1
Falk Hassler (University of Oviedo)
“Poisson-Lie T-Duality in Double Field Theory”
abstract (click to view) A formulation of Double Field Theory is presented which makes Poisson-Lie T-duality manifest. It allows to identify the doubled space with a Drinfeld double and provides a powerful tool to extract the transformation of the metric, B-field, dilaton and R/R potentials under Poisson-Lie T-duality. Its application to integrable deformations is discussed. (click to hide)
Thu
22.11.
16:00
HIT J 53
Giulio Salvatori (University of Milan)
“Positive geometries for 1-loop Integrands”
abstract (click to view) In past years we have witnessed remarkable progresses in the computation of scattering amplitudes. On the one hand, these progresses allowed to compute amplitudes that seemed previously intractable. On the other hand, they exposed remarkable mathematical structures, intimately tied to the S-matrix, and which offer non conventional understandings of the latter. An example of these new ideas is the Amplituhedron, a sort of polytope that encodes in the combinatorial structure of its boundaries the analytical properties of the S-matrix for N=4 SYM. Remarkably, similar objects - called generalised Associahedra - have been recently individuated for the much simpler bi-adjoint scalar field theory, up to 1-loop level. The aim of this talk is to give a self-contained introduction to these new developments. First, we will give a review of polytopes and their canonical differential forms. Then we will see how 1-loop integrands can be obtained from the differential form of Associahedra. As an application of this approach, we will discuss a new recursive formula inspired by geometry, which would be difficult to prove - let alone imagine - using standard methods of Quantum Field Theory. (click to hide)
Mon
26.11.
11:30
HIT E41.1
Du Pei (Aarhus University & Caltech)
“6d (1,0) theory, 4-manifolds and topological modular forms”
Wed
28.11.
11:00
HIT E41.1
Benjamin Basso (ENS Paris)
“Continuum limit of fishnet graphs and AdS sigma model”
abstract (click to view) I will talk about the thermodynamical limit of planar fishnet graphs in 4d. Using techniques developed for studying scaling dimensions of single trace operators in N=4 SYM, I will argue that fishnet graphs are described in the continuum limit by the 2d AdS5 non-linear sigma model. (click to hide)
Wed
05.12.
11:00
HIT E41.1
Fabian Ruehle (University of Oxford)
“SU(3) structure and Calabi-Yau manifolds”
Wed
12.12.
11:00
HIT E41.1
Daniel Medina Rincon (ETH Zurich)
“Holographic Wilson loops: Quantum string corrections”
abstract (click to view) In the gauge-string correspondence Wilson loops have a known physical description at both sides, making them ideal probes for the duality. Localization has lead to predictions at all orders in the coupling for certain Wilson loop configurations in supersymmetric field theories. String calculations at strong coupling have proved surprisingly difficult and have only been successful at leading order and, in very rare cases, next-to-leading order in perturbation theory. I will present recent progress in the string theory computation of Wilson loops in N=4 and N=2* SYM theories, and their matching with predictions from localization. (click to hide)
Wed
19.12.
11:00
HIT E41.1
Daniele Dorigoni (Durham University)
“Cheshire cat resurgence in supersymmetric QM and QFT”
abstract (click to view) We start by reviewing some background material on Borel transform and resurgent analysis, emphasising their importance in standard perturbation theory for physical observables. We then specialise our discussion to some simple supersymmetric quantum mechanical model, showing how resurgence can be applied also in the case of a truncating, or even vanishing perturbative expansion in a nice example of what is called Cheshire cat resurgence. We continue with a two-dimensional quantum field theory example studying the prototypical CP^{N-1} model with N=(2,2) supersymmetry. After having computed the two-sphere partition function of this model via susy-localisation we show how Cheshire cat resurgence appears also in this quantum field theory example, allowing us to reconstruct non-perturbative physics even in the case of a truncating perturbative expansion. (click to hide)

last modified: Thu, 20 Dec 2018, 15:02 CET

Spring Semester 2019

Wednesday, 11:30, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel, Blagoje Oblak, Hagen Münkler

day
date
time
venue
speaker
title
Wed
13.02.
11:30
HIT E41.1
Piotr Kucharski (Caltech)
“Knots-quivers correspondence - a physical perspective”
Wed
06.03.
11:30
HIT E41.1
Leonardo Rastelli (CERN)
“The chiral algebra program for 4d superconformal field theories”
Mon
11.03.
16:45
HIT H42
Henning Samtleben (ENS Lyon)
Theoretical Physics Colloquium: “Exceptional Geometry and String Compactifications”
abstract (click to view) Generalised and exceptional geometry have emerged over recent years as underlying structures and powerful tools in string theory and supergravity. They give a new twist to Kaluza’s old idea of geometrising gauge interactions by the introduction of additional spatial dimensions. The extended nature of the fundamental objects gives rise to a natural “stringy” generalisation of Riemannian geometry which is based on the exceptional duality groups appearing in string/M-theory. This has led to remarkable progress in the study of string and gravity compactifications. (click to hide)
Wed
13.03.
11:30
HIT E41.1
Michele Schiavina (ETH Zurich)
“Field theory on manifolds with boundary”
Wed
20.03.
11:30
HIT E41.1
Thomas Mertens (Gent U.)
“Jackiw-Teitelboim gravity and the Schwarzian”
abstract (click to view) We derive Schwarzian correlation functions using the BF formulation of Jackiw-Teitelboim gravity, where bilocal operators are interpreted as boundary-anchored Wilson lines in the bulk. Crossing Wilson lines are associated with OTO-correlators and give rise to 6j-symbols. We discuss the semi-classical bulk black hole physics contained within the correlation functions. Extensions including bulk defects related to the other coadjoint orbits are discussed. (click to hide)
Wed
27.03.
11:30
HIT E41.1
Timo Weigand (Heidelberg U.)
“Modularity and the Weak Gravity Conjecture in Various Dimensions”
abstract (click to view) A number of so-called Swampland Conjectures have been put forward in the literature to describe constraints which every effective theory with a consistent coupling to quantum gravity should obey. String Theory offers a unique opportunity to put these general ideas to a quantitative test in a well-controlled computational framework. Among the earliest such conjectures in the Weak Gravity Conjecture: Every gauge theory coupled to gravity should contain certain particles whose charge-to-mass ratio exceeds that of extremal charged black holes. According to more refined versions, these super-extremal states form a tower which becomes exponentially light in the weak coupling regime. We will explicitly test this conjecture for non-perturbative string (more precisely F-theory/heterotic) compactifications to six and four dimensions with eight and, respectively, four supercharges. The mathematics behind the super-extremality condition is tied to modular properties of the elliptic genera of critical strings which become tensionless in the weak coupling regime, and makes further contact with mirror symmetry and BPS state counting via Gromov-Witten invariants. In six dimensions, the tower of super-extremal states is found to form a sublattice specified by the geometry of the compactification, while in four dimensions the properties of the non-perturbative elliptic genera depend on the choice of background flux. (click to hide)
Wed
03.04.
11:30
HIT E41.1
Lorenzo Bianchi (Queen Mary University)
“Shape deformations of superconformal defects”
abstract (click to view) Deformations in the shape of an extended probe are related to the so-called displacement operator. After reviewing the role of such operator in the general theory of conformal defects, I will discuss the example of N=2 theories in four dimensions, highlighting a general pattern relating shape deformations to a modification of the background geometry. I will then discuss the available techniques for the exact computation of such deformations. (click to hide)
Wed
10.04.
11:30
HIT E41.1
Jeremias Aguilera Damia (La Plata University)
“Aspects of TT deformation”
abstract (click to view) This is an attempt to make an extensive review of the progress
achieved by studying a particular flow in the space of theories, driven by
an irrelevant operator made up from the stress-energy tensor. This special
flow comes up with some interesting and novel features, and turns out to
pose a convenient frame for approaching general topics of great relevance
in the context of High Energy Physics, as the emergence of gravity,
relations with string theory, as well as a novel extension of the
holographic diccionary. (click to hide)
Wed
17.04.
11:30
HIT E41.1
Sven Krippendorf (Munich U.)
“Machine learning as a tool for theoretical particle physicists”
Wed
08.05.
11:30
HIT E41.1
Saskia Demulder (Vrije U., Brussels)
“Poisson-Lie T-duality and integrable deformations”
abstract (click to view) The property of integrability usually requires the presence of a very large number of symmetries and as such is a very rare property of physical models.
Deformations of integrable models challenge our understanding of integrability as these constitute whole families of integrable models with reduced
symmetries. Recently, it came to light that particular classes of integrable deformations can be related to one another using Poisson-Lie T-duality.
This talk will focus on how this generalised notion of T-duality can be made manifest within double field theory. This formalism offers a powerful and
provides a systematic way of investigating SUGRA backgrounds of integrable deformations. (click to hide)
Wed
15.05.
11:30
HIT E41.1
Riccardo Borsato (Santiago de Compostela U., IGFAE)
“Marginal deformations of WZW models and the classical Yang-Baxter equation”
abstract (click to view) After reviewing the relevant subjects, I will discuss how so-called Yang-Baxter deformations of sigma models (based on an R-matrix solving the classical Yang-Baxter equation) can be used to generate marginal current-current deformations of Wess-Zumino-Witten models. For non-compact groups these marginal deformations are more general than the ones usually considered, since they can involve a non-abelian current subalgebra. I will focus on the application of these deformations to the AdS3 x S3 string. (click to hide)
Wed
22.05.
11:30
HIT E41.1
Sasha Zhiboedov (CERN)
“The light-ray OPE, event shapes and superconvergence”
Mon
27.05.
16:45
HIT H42
Astrid Eichhorn (Universität Heidelberg)
Theoretical Physics Colloquium: “Asymptotic Safety: Towards a new Paradigm for the Fundamental Building Blocks of Nature”
abstract (click to view) What are the fundamental building blocks of matter and what is the microscopic quantum structure of spacetime? In this talk I will explain how an asymptotically safe answer to these questions could look like. Asymptotic safety underlies a candidate theory of quantum gravity. I will explain the key idea and review the status of the field, highlighting potential implications for black-hole physics. Moreover, I will explain how the asymptotic safety paradigm could extend to the Standard Model of particle physics, providing a unified, predictive theory of all fundamental interactions. (click to hide)
Tue
28.05.
12:45
HIT E41.1
Evgeny Skvortsov (MPI Potsdam)
“Quantum Gravity via Higher Spins and Three-dimensional Bosonization Duality”
abstract (click to view) Hypothetical Higher Spin Gravities are supposed to be minimalistic extensions of gravity that embed it into a quantum consistent theory. However, such minimality turns out to be in tension with the field theory approach, as well as with the numerous no-go theorems. We report on the recent progress in constructing Higher Spin Gravities and testing quantum effects therein. The same time, via AdS/CFT Higher Spin Gravities should be related to a variety of interesting three-dimensional CFT's from ABJ to the Ising model. These CFT's were conjectured to exhibit a number of remarkable dualities, in particular, the three-dimensional bosonization duality. We show how Higher Spin Gravity can be useful to prove the bosonization duality at least in the large N limit. (click to hide)
Thu
20.06.
11:30
HIT E41.1
Shiroman Prakash (Dayalbagh Educational Institute)
“Tensor Models in Higher Dimensions”
abstract (click to view) Tensor models are theories with fields having more than two indices. Examples include theories with O(N)^3 symmetry. Such theories lead to new large N limits, different from the more familiar vector model and adjoint large N limits, as we will explain in detail in the talk. These large N limits have a great deal of formal similarity with the SYK model, although there are important physical differences. While large N tensor models exist in 0d and 1d, the question of whether it is possible to construct interacting conformal tensor models in higher dimensions is still open. We will describe previous attempts at constructing such theories and why they fail. (click to hide)
Fri
21.06.
14:00
HIT E41.1
Barak Kol (Hebrew University of Jerusalem)
“Towards a general theory for evaluating Feynman diagrams”
abstract (click to view) Feynman integrals are at the computational core of quantum field theory, yet despite over 70 years of rich experience, it is probably fair to say that a general theory for their evaluation is lacking. The talk will describe certain steps towards this goal. We shall consider a Feynman diagram of fixed topology (a graph) as a function of all possible parameters (kinematical invariants, masses, numerators, spacetime dimension) and associate with it a system of partial differential equations. The system is associated with a continuous group which is naturally associated with the graph, and its orbits foliate the parameter space. The equation system allows to reduce the diagram to a line integral over simpler diagrams: diagrams gotten by contracting a propagator. (click to hide)

last modified: Mon, 2 Sep 2019, 15:18 CEST

Fall Semester 2019

Wednesday, 11:30, HIT E41.1

Organised by: Niklas Beisert, Matthias Gaberdiel, Daniel Medina, Hagen Münkler

day
date
time
venue
speaker
title
Wed
18.09.
11:30
HIT E41.1
Christian Ferko (University of Chicago)
“T Tbar and Supercurrent-Squared”
abstract (click to view) The T Tbar deformation of 2D QFTs offers a rare example of an irrelevant deformation where one has some control over the deformed theory. In addition, T Tbar has tantalizing connections to string theory -- the T Tbar deformation of a free scalar, for instance, gives the Nambu-Goto action. It is natural to wonder whether this deformation can be generalized to higher dimensions, although the most straightforward higher-dimensional analogue lacks the magical properties of the two-dimensional version.
In this talk, I will present a manifestly supersymmetric version of T Tbar, called "supercurrent-squared," which can be defined for SUSY field theories in any number of dimensions. There is some evidence -- such as the relationship between 4D supercurrent-squared and the SUSY DBI action -- that this deformation has properties similar to those of T Tbar in higher-dimensional theories. I will also discuss connections between supercurrent-squared and nonlinearly realized supersymmetry, which suggests that these deformations are related to spontaneous symmetry breaking. (click to hide)
Wed
02.10.
11:30
HIT E41.1
Kasia Rejzner (York University)
“Perturbative algebraic quantum field theory – a new paradigm for perturbative QFT”
abstract (click to view) In this talk I will present the framework of perturbative algebraic quantum field theory (pAQFT), which is a mathematically rigorous formulation of perturbative QFT, inspired by the local quantum physics paradigm of Haag and Kastler. In recent years this framework has been successfully applied to QFT on curved spacetimes and can even be used to study some features of quantum gravity. (click to hide)
Tue
08.10.
11:30
HIT E41.1
Stefano Massai (ETH Zürich)
“Phases of little string theory and fuzzballs”
abstract (click to view) Resolved A-type singularities admit an exact description in worldsheet string theory that regularises the linear dilaton throat dual to little string theory. A generalisation of this mechanism offers a weakly coupled description of “fuzzball” states in the Hilbert space of two and three-charge black holes. These constructions reveal stringy excitations that become light at the threshold of horizon formation and provide a glimpse of the entropic long string sector in the gravity regime. A unifying twelve dimensional description of black hole microstates emerges. (click to hide)
Wed
16.10.
11:30
HIT E41.1
Adwait Gaikwad (Tata Institute)
“Gravitational collapse in SYK models and Choptuik-like phenomenon”
Tue
22.10.
11:30
HIT E41.1
Oleg Evnin (Chulalongkorn University)
“Resonant weakly nonlinear dynamics in AdS”
abstract (click to view) The fully resonant spectrum of normal mode frequencies for linearized
fields in Anti-de Sitter spacetime (AdS) leads to an enhancement of
nonlinear interactions, so that arbitrarily small nonlinearities may
produce large effects if one waits long enough. For gravitating
perturbations, this is believed to lead to black hole formation
starting from arbitrarily small perturbations in some cases. The
problem has attracted a considerable amount of attention due to its
role as a dual picture for holographic thermalization in conformal
field theories (CFTs) on spheres, its conceptual importance in
mathematical general relativity, and its connection to studies of
turbulent nonlinear flows of energy in contemporary PDE mathematics.
Close parallels exist with dynamics of nonlinear wave equations in
AdS, and with nonlinear Schrödinger equations in harmonic potentials,
the latter being of significance for condensed matter physics.
I will describe the resonant approximation that accurately captures
the relevant dynamics of nonlinear AdS problems over long (but
limited) times in the weakly nonlinear regime. I will then present a
few characteristic behaviors of the resulting resonant systems: finite
time turbulent blow-ups that encode black hole formation in general
relativity, Fermi-Pasta-Ulam-like returns of energy that very
accurately (but not exactly) reconstruct the initial configuration and
would present an obstruction to thermalization in dual CFTs, and cases
where special exact solutions of the resonant system can be obtained,
exhibiting exactly periodic sequences of direct and reverse cascades
of energy. (click to hide)
Wed
23.10.
11:15
HIT E41.1
Dmitry Galakhov (MIPT Moscow)
“BPS Hall algebra of scattering Hall states”
abstract (click to view) Starting with a very pedestrian point of view we compare two
different at the first glance definitions for an algebra associated to
BPS states in supersymmetric fields theories. One proposed by Harvey and
Moore exploits scattering matrices of BPS states as structure constants of
a new algebra. Another one proposed by Kontsevich and Soibelman gives a
construction according to the structure of cohomological Hall algebras.
We show these two constructions give equivalent algebras. (click to hide)
Wed
30.10.
16:00
HIT F22
Dalimil Mazac (YITP Stony Brook)
“Sphere packing, modular bootstrap and extremal functionals”
abstract (click to view) I will prove a new theorem about 2D CFTs: Every unitary 2D CFT
must contain a non-trivial Virasoro primary of scaling dimension at most
c/8 + 1/2, where c is the central charge. At large c, this is an
improvement of the Hellerman bound c/6 + O(1), and is relevant for
constraining the spectrum of gravitational theories in AdS3. The proof
follows from the modular bootstrap and uses analytic extremal functionals,
originally developed in the context of four-point SL(2) conformal
bootstrap. In the second part of the talk, I will discuss a surprising
connection between modular bootstrap and the sphere-packing problem from
discrete geometry. In particular, the above bound on the gap becomes a
bound on the sphere-packing density. In 8 and 24 dimensions, this bound is
sharp and leads to a solution of the sphere-packing problem in these
dimensions, as originally proved by Viazovska et al. Time allowing, I will
discuss a generalization of the analytic functional method to
higher-dimensional CFTs. (click to hide)
Mon
04.11.
16:45
HIT H42
Thomas Fischbacher (Google Research Zürich)
Theoretical Physics Colloquium: “Studying Spontaneous Symmetry Breaking with Machine Learning Tools”
abstract (click to view) Modern Machine Learning software libraries such as Google's TensorFlow can be employed to greatly simplify the analysis of high-dimensional scalar sectors of some M-Theory compactifications. This talk gives an overview over recent insights into the structure of N=8 SO(8) de Wit-Nicolai Supergravity that have been obtained in this way. We will also look into using readily available Google Research tools to easily obtain new results by modifying pedagogical code examples that have been published alongside our recent comprehensive study of SO(8) supergravity equilibria. (click to hide)
Tue
05.11.
11:30
HIT E41.1
Marc-Antoine Fiset
“Superconformal algebras for twisted connected sums and G2 mirror symmetry”
abstract (click to view) Early hints of mirror symmetry for Calabi-Yau manifolds arose from studying
the algebra of chiral symmetries of the worldsheet theory describing
strings on these geometries. In 1809.06376
<https://arxiv.org/abs/1809.06376>, which the talk will be about, I perform
a similar analysis, replacing Calabi-Yau manifolds by 7-dimensional G2
holonomy spaces constructed via the twisted connected sum method of Corti,
Haskins, Nordström, and Pacini. Besides connecting nicely with recent
results on the conjectured mirror symmetry for G2, this work is a necessary
step for applications of twisted connected sums in string theory. (click to hide)
Wed
06.11.
11:30
HIT E41.1
Sylvain Lacroix (Universität Hamburg)
“Integrable coupled sigma-models from affine Gaudin models”
abstract (click to view) In this seminar, I will discuss integrable systems called affine Gaudin models and their application to the study of integrable sigma models. As an introductory example, I will first discuss a simpler class of Gaudin models, the finite ones, and their relation with integrable spin chains and mechanical systems. I will then explain how to use affine Gaudin models to construct new integrable classical sigma models, by coupling together an arbitrary number of principal chiral models with Wess-Zumino terms. (click to hide)
Wed
13.11.
11:30
HIT E41.1
Nat Levine (Imperial College)
“Integrable sigma models and 2-loop RG flow”
abstract (click to view) It is often suggested that integrable 2d sigma models should be renormalizable, however this relationship has only previously been checked in the 1-loop approximation. The aim of this work is to understand what happens beyond 1-loop. Based on the examples of the lambda- and eta-models, we confirm that classically integrable models appear to be 2-loop renormalizable if supplemented with particular finite local counterterms, i.e. quantum corrections to the target space geometry. The lambda-model is further studied as a sigma model on a "tripled" target space where extra symmetries become manifest, enforcing renormalizability without the need for extra counterterms. Its 2-loop beta-function is computed, matching the known results for groups and symmetric spaces in the limit when the lambda-model becomes the corresponding non-abelian dual model. This leads to the statement that non-abelian duality commutes with the RG flow beyond 1-loop order. (click to hide)
Wed
20.11.
11:45
HIT E41.1
Usman Naseer (MIT / Uppsala University)
“On the UV-finiteness of entanglement entropy in string theory”
abstract (click to view) Entanglement entropy in a local quantum field theory with a background
spacetime suffers from UV divergences. Arguments based on black hole
physics, however, suggest that entanglement entropy in a quantum theory of
gravity should be finite. We use string field theory to study properties of
entanglement entropy in string theory and show that the entanglement
entropy of closed bosonic strings is UV-finite. (click to hide)
Tue
26.11.
11:45
HIT E41.1
Nicolai Reshetikhin (University of California Berkeley)
“Semiclassical eigenfunctions of quantum integrable systems and the Poisson sigma model”
abstract (click to view) Poisson sigma model is a two dimensional topological field theory with the target being a Poisson manifold. As it was shown by Cattaneo and Felder,
the partition function with certain boundary conditions gives the Kontsevich's star product quantization of functions on the target Poisson manifold. In the talk I will explain how a different choice of boundary conditions gives semiclassical expansion of eigenfunctions of any given quantum integrable
system. (based on ongoing work with A. Cattaneo and P. Mnev). (click to hide)
Wed
27.11.
10:30
HIT F22
Fedor Levkovich-Maslyuk (ENS Paris)
“Towards Structure Constants in N=4 SYM via Quantum Spectral Curve”
abstract (click to view) The Quantum Spectral Curve (QSC) is a powerful integrability-based
framework capturing the nonperturbative spectrum of planar N=4 SYM theory.
We present first evidence that it should also play an important role for
computing exact correlation functions. We compute the correlator of 3
scalar local operators connected by Wilson lines forming a triangle in the
ladders limit, and show that it massively simplifies when written in terms
of the QSC. The final all-loop result takes a very compact form, suggesting
its interpretation via Sklyanin's separation of variables (SoV). We discuss
work in progress on extending these results to local operators. We also
derive, for the first time, the SoV measure for su(N) noncompact and
compact spin chains. (click to hide)
Wed
04.12.
11:45
HIT F22
Volker Schomerus (DESY Hamburg)
“Integrability of Conformal Partial Wave Expansions”
Wed
11.12.
11:45
HIT F22
Alejandra Castro (University of Amsterdam)
“The Holographic Landscape of Symmetric Product Orbifolds”
abstract (click to view) I will discuss the application of Siegel paramodular forms to constructing new examples of holography. These forms are relevant to investigate the growth of coefficients in the elliptic genus of symmetric product orbifolds at large central charge. The main finding is that the landscape of symmetric product theories decomposes into two regions. In one region, the growth of the low energy states is Hagedorn, which indicates a stringy dual. In the other, the growth is much slower, and compatible with the spectrum of a supergravity theory on AdS3. I will provide a simple diagnostic which places any symmetric product orbifold in either region. The examples I will present open a path to novel realizations of AdS3/CFT2. (click to hide)
Wed
18.12.
11:45
HIT F22
Yolanda Lozano (University of Oviedo)
“Recent progress in AdS3/CFT2”
abstract (click to view) We will discuss a recent classification of AdS3 solutions with (0,4) supersymmetry and propose 2d CFTs dual to them. (click to hide)

last modified: Thu, 2 Jan 2020, 16:40 CET

Spring Semester 2020

Wednesday, 11:45, zoom: 301-229-497

Organised by: Niklas Beisert, Matthias Gaberdiel, Daniel Medina, Hagen Münkler

day
date
time
venue
speaker
title
Wed
25.03.
15:30
zoom: 301-229-497
Scott Collier (Harvard University)
“Virasoro analytic bootstrap and universal dynamics in CFT₂”
Wed
01.04.
11:45
zoom: 301-229-497
Carlo Heissenberg (Nordita)
“Asymptotic symmetries: higher spins and higher dimensions”
abstract (click to view) The interplay between asymptotic symmetries and their observable counterparts, soft theorems and memory effects, has recently drawn renewed attention on the asymptotic properties of gauge theories near null infinity. We present recent developments in the analysis of such properties for higher dimensions and for theories possessing fields with arbitrary integer spin. Our discussion is mainly motivated by the fact that Weinberg’s soft theorem holds for arbitrary spins and dimensions. In this context, we focus on the possibility of introducing infinite-dimensional asymptotic symmetries whose Ward identities give rise to the soft theorem, compatibly with the finiteness of physical observables at infinity, and residual symmetries which are suited to the interpretation of memory effects as vacuum transitions. (click to hide)
Wed
08.04.
11:45
zoom: 301-229-497
Evgeny Sobko (Southampton University)
“Large N and Double-Scaling Limit in Principal Chiral Model: a New Non-Critical String?”
abstract (click to view) I will present a systematic, non-perturbative analysis of the
two-dimensional SU(N) Principal Chiral Model (PCM) in the large-N limit.
Starting with the known infinite-N solution for the ground state at fixed
chemical potential, we devise an iterative procedure to solve the Bethe
ansatz equations order by order in 1/N. The first few orders, which are
explicitly computed, reveal a systematic enhancement pattern at strong
coupling calling for the near-threshold resummation of the large-N
expansion. The resulting double-scaling limit bears striking similarities
to the c=1 non-critical string theory and suggests that the double-scaled
PCM is dual to a non-critical string with a 2+1-dimensional target space
where an additional dimension emerges from the SU(N) Dynkin diagram. (click to hide)
Wed
15.04.
11:45
zoom: 301-229-497
Shouvik Datta (UCLA & ETH Zurich)
“Eigenstate thermalization and Virasoro symmetry”
abstract (click to view) Two dimensional conformal field theories have an infinite number of
conserved charges and, at the same time, are dual to 3d gravity which
admits black hole solutions. This leads to a puzzle on how the
thermalization process can occur. We address universal aspects of this
question which can be leveraged by using Virasoro symmetry alone. It turns
out that matrix elements of light probes in typical high-energy descendant
states have the right properties to ensure compatibility with the weak
version of the Eigenstate Thermalization Hypothesis (ETH). The tools
developed along the way also enable us to directly prove the property of
conformal blocks exponentiating in the semi-classical regime. (click to hide)
Wed
22.04.
10:45
zoom: 301-229-497
Ivan Kostov (CEA Saclay)
“The Octagon Form Factor in N=4 SYM”
abstract (click to view) The computation of a certain class of four-point functions of heavily charged BPS operators boils down to the computation of a special form factor - the octagon - obtained by gluing together two hexagon form factors. The octagon represents an infinite sum over the mirror magnons circulating between the two hexagons. The sum resembles a Coulomb gas and can be repackaged as an expectation value in the Fock space of chiral fermions. This gives a representation of the octagon as a Fredholm pfaffian. Due to a doubling phenomenon the Fredholm pfaffian is in fact a Fredholm determinant. In this text I will review the main analytical techniques to handle this determinant, which allow to build systematically the weak and the strong coupling expansions of the octagon. The talk is based on the works [1–8]
References:
1. F. Coronado, “Bootstrapping the simplest correlator in planar N=4 SYM at all loops,”hep-th/1811.03282.
2. F. Coronado, “Perturbative four-point functions in planarN=4SYM from hexagonalization,”JHEP01(2019) 056,hep-th/1811.00467.
3. I. Kostov, V. B. Petkova, and D. Serban, “Determinant formula for the octagon form factor in N=4SYM,”1903.05038.
4. I. Kostov, V. B. Petkova, and D. Serban, “The Octagon as a Determinant,”1905.11467.
5. T. Bargheer, F. Coronado, and P. Vieira, “Octagons I: Combinatorics and Non-Planar Resummations,”1904.00965.
6. T. Bargheer, F. Coronado, and P. Vieira, “Octagons II: Strong Coupling,”1909.04077.
7. A. V. Belitsky and G. P. Korchemsky, “Exact null octagon,”1907.13131.
8. A. V. Belitsky and G. P. Korchemsky, “Octagon at finite coupling,”2003.01121. (click to hide)
Wed
06.05.
10:45
zoom: 301-229-497
Jan Manschot (Trinity College Dublin)
“Topological correlators in supersymmetric gauge theory”
abstract (click to view) I will discuss topological correlators in 4d, N=2 supersymmetric gauge theory with gauge group SU(2). On an Euclidean, compact space-time, the contribution of the Coulomb branch to these correlators reduces to an integral over the effective coupling constant. Motivated by the decoupling of BRST exact observables, I will put forward a new prescription for the regularization and evaluation of these correlators. Joint work with G. Korpas, G. Moore, and I. Nidaiiev. (click to hide)
Wed
13.05.
16:00
zoom: 301-229-497
Aldo Riello (Perimeter Institute)
“The quasi-local degrees of freedom of Yang-Mills theory”
abstract (click to view) Gauge theories possess nonlocal features that, in the presence of boundaries, inevitably lead to subtleties. In particular their fundamental degrees of freedom are not point-like. This leads to a non-trivial cutting (C) and sewing (S) problem: (C) Which gauge invariant degrees of freedom are associated to a region with boundaries? (S) Do the gauge invariant degrees of freedom in two complementary regions R and R’ unambiguously comprise *all* the gauge-invariant degrees of freedom in M = R ∪ R’ ? Or, do new “boundary degrees of freedom” need to be introduced at the interface S = R ∩ R’ ? In this talk, I will address and answer these questions in the context of Yang-Mills theory. The analysis is carried out at the level of the symplectic structure of the theory, i.e. for linear perturbations over arbitrary backgrounds. I will also discuss how the ensuing results hint towards a quasilocal derivation of the superselection of the electric flux through the boundary of a region, and into a novel gluing formula which constructively proves that no ambiguity exists in the gluing of regional gauge-fixed configurations. Time allowing I will also address how the formalism generalizes the “Dirac dressing” of charged matter fields, and how, in the presence of matter, quasi-local “global” charges (as opposed to gauge charges) emerge at symmetric (i.e. reducible) configurations.
This talk is based on arXiv:1910.04222, with H. Gomes (U. of Cambridge, UK).
See also arXiv:1808.02074, with H. Gomes and F. Hopfmüller (Perimeter) (click to hide)
Wed
20.05.
10:45
zoom: 301-229-497
Alba Grassi (CERN)
“Extremal correlators and Random Matrix Theory”
Wed
27.05.
10:45
zoom: 301-229-497
Andrea Puhm (Ecole Polytechnique)
“Infrared aspects of gravity and flat space holography”
abstract (click to view) The realization that soft theorems in gauge theory and gravity are manifestations of Ward identities for asymptotic symmetries has reinvigorated recent attempts at flat space holography. One of the key milestones from applying this paradigm is that it solidifies a conjectured extension of the BMS group to include superrotations, based on a newly discovered subleading soft graviton theorem. This precipitated two parallel initiatives within the field. On the one hand, the subleading soft graviton mode is a natural stress tensor candidate for a putative dual celestial CFT with a Virasoro symmetry, which provoked reexamining scattering amplitudes in a basis that makes conformal covariance manifest. On the other hand, the correspondence between the subleading soft graviton theorem and the proposed asymptotic Virasoro superrotation symmetry does not appear to be bijective and an extension to arbitray diffeomorphisms on the celestial sphere was suggested. In this talk I will provide a unified treatment of conformally soft Goldstone modes of spontaneously broken asymptotic symmetries which will land us at the crossroads of the two ongoing debates about what the appropriate conformal basis for celestial CFT is and what the asymptotic symmetry group of Einstein gravity at null infinity should be. (click to hide)
Wed
03.06.
10:45
zoom: 301-229-497
Stefan Hohenegger (Université de Lyon)
“Symmetries in A-Type Little String Theories”
abstract (click to view) In this talk, I discuss Little String Theories (LSTs), which are a type of interacting quantum theories whose UV-completion contains string-like (i.e. extended) degrees of freedom without gravitation. I focus on the so-called A-type LSTs, which can be described in M-theory through N parallel M5-branes arrayed on a circle or through F-theory compactified on a toric Calabi-Yau threefold. I argue that these LSTs allow for various dual low energy limits, describing quiver gauge theories with different gauge- and matter content. These dualities in turn imply a dihedral symmetry for any individual such theory, which acts intrinsically non-perturbative from the gauge theory perspective. Exploiting this symmetry I provide evidence for numerous interesting structures of the free energy, notably a decomposition of the leading instanton order, which is reminiscent of (effective) Feynman diagrams. The effective coupling functions appearing in this fashion show certain similarities with so-called modular graph functions, which have appeared in the study of Feynman amplitudes in string- and field theory. (click to hide)

last modified: Mon, 25 May 2020, 10:33 CEST

Fall Semester 2020

Tuesday, 16:00, zoom: 940 4378 1498

Organised by: Niklas Beisert, Matthias Gaberdiel, Marc-Antoine Fiset, Pietro Longhi

day
date
time
venue
speaker
title
Tue
29.09.
16:00
zoom: 940 4378 1498
Jakub Vosmera (ETH Zurich)
“Exploring novel open string boundary conditions with string field theory”
abstract (click to view) We will first give a brief overview of open (super)string field theory and discuss how its classical solutions can be used to extract information about open string backgrounds (D-branes) for a given closed string worldsheet CFT. We will then analyze two particular settings where this approach sheds new light on non-trivial conformal boundary conditions: new exotic D-branes wrapping a 2-torus in the bosonic string and D(-1)/D3 bound states wrapping a 4-torus in type II superstring. (click to hide)
Tue
06.10.
16:00
zoom: 940 4378 1498
Francesco Galvagno (ETH Zurich)
“Emitted radiation and geometry”
abstract (click to view) We discuss the computation of the radiated energy by an accelerated heavy particle. This quantity is captured by the one-point function of the stress energy tensor in presence of a Wilson line. In N=2 superconformal theories we prove that this observable is exactly related to a small deformation of the background geometry, just by a consistent implementation of the symmetries. In a four dimensional case, SUSY localization allows to express the emitted energy in terms of a matrix model on a squashed sphere. Finally we analyze the consequences of our results for a weak coupling perturbative expansion. (click to hide)
Tue
13.10.
16:00
zoom: 940 4378 1498
Alexander Maloney (McGill)
“Gravity from Averaging CFTs”
abstract (click to view) I will explore the idea that certain theories of gravity in Anti-de Sitter space are dual to an average over an ensemble of quantum theories, rather than to a specific quantum theory. I will describe an average over Narain’s family of two-dimensional conformal field theories which describe free bosons on a torus, and compute the partition function using the Siegel-Weil formula. The result takes the form of a sum over geometries as one would expect in a theory of gravity. But the gravitational theory looks more like a Chern-Simons theory than like Einstein gravity. (click to hide)
Tue
20.10.
16:00
zoom: 940 4378 1498
Luigi Tizzano (Stony Brook & SCGP)
“Delayed Deconfinement and the Hawking-Page Transition”
abstract (click to view) We revisit the confinement/deconfinement transition in N=4 super Yang-Mills (SYM) theory and its relation to the Hawking-Page transition in gravity. Recently there has been substantial progress on counting the microstates of 1/16-BPS extremal black holes. In this context, we discuss a phenomenon in complex matrix models which we call "delayed deconfinement". It turns out that when the action is complex, due to destructive interference, tachyonic modes do not necessarily condense. We demonstrate this phenomenon in a simple unitary matrix model and finally in the context of N=4 SYM. Delayed deconfinement implies a first-order transition, in contrast to the more familiar cases of higher-order transitions in unitary matrix models. We determine the deconfinement line and find remarkable agreement with the prediction of gravity. (click to hide)
Tue
03.11.
16:00
zoom: 940 4378 1498
Shlomo Razamat (Technion)
“Where do supersymmetric dualities come from?”
abstract (click to view) We will overview the program of realizing supersymmetric quantum field theories in 4d by compactifying 6d SCFTs on Riemann surfaces. In particular we will discuss how strong coupling IR phenomena in 4d, such as dualities and emergence of global symmetries, can be understood geometrically through such compactification constructions. As a concrete example we will show that the 4d SU(N+2) SQCD in the middle of the conformal window can be engineered by compactifying certain 6d SCFTs on three punctured spheres. We will discuss here the interplay between simple geometric and group theoretic considerations and complicated field theoretic strong coupling phenomena. In particular we will show how many known and novel dualities and symmetry enhancement phenomena of supersymmetric gauge theories with SU(M) type gauge groups are related to the Weyl group of SO(12+4N). (click to hide)
Tue
10.11.
16:00
zoom: 940 4378 1498
Marcos Marino (Geneva)
“Resurgence, BPS states, and quantum knot invariants”
abstract (click to view) Resurgent analysis associates, to a perturbative series, a rich structure of exponentially small corrections, or trans-series. Recent developments indicate that, in some cases, this structure encodes the counting of BPS states in an appropriate quantum theory. After reviewing some background material, I will
focus on the resurgent structure of the perturbative Chern-Simons invariants of hyperbolic knots. In this example, singularities in the Borel plane appear in infinite towers, and the corresponding Stokes constants are integer numbers. This gives a new mechanism for obtaining integer invariants in these theories. I present various conjectures/computations of these integers, which appear as coefficients of q-series, and I relate them to BPS invariants of hyperbolic knots. State integrals and their holomorphic blocks play an important role in the story. (click to hide)
Tue
17.11.
16:00
zoom: 940 4378 1498
Manus Visser (Geneva)
“Gravitational Thermodynamics of Causal Diamonds”
abstract (click to view) Black hole (more generally, horizon) thermodynamics is a window into quantum gravity. In this talk I discuss whether horizon thermodynamics can be quasi-localized. A special case is the static patch of de Sitter space, known since the work of Gibbons and Hawking to admit a thermodynamic equilibrium interpretation. I will review this example, and present its generalization to finite causal diamonds in maximally symmetric spacetimes. This story includes a Smarr formula and first law of causal diamonds, analogous to those of black hole mechanics. I will also give a holographic interpretation of the first law of causal diamonds in AdS3/CFT2, in terms of differential entropy and holographic complexity. (click to hide)
Tue
24.11.
16:00
zoom: 940 4378 1498
Matthias Volk (Niels Bohr Institute)
“One-point functions in defect CFTs with holographic duals”
abstract (click to view) In conformal field theories with defects (dCFTs) one-point functions of scalar operators constitute interesting observables. In this talk we discuss dCFTs that have a dual holographic description in terms of probe brane systems, in particular the D3-D5 and D3-D7 probe brane intersections. We describe how the non-trivial vacuum expectation values of the scalars in the dCFT lead to a mixing problem in the quadratic terms of the Lagrangian that can be solved by coupling group representations, thereby reviewing the work of arXiv:1611.04603 for the D3-D5 system. For the D3-D7 system we explain how similar methods allow us to prepare the dCFT for perturbative calculations by deriving the propagators for the theory. As an application we compute the one-loop one-point function of the scalar operator tr(Z^L) finding agreement with a holographic computation in a certain double-scaling limit. We comment on the connection to recent progress in the integrability of one-point functions in which the latter are expressed in terms of overlaps of Bethe eigenstates with matrix product states.
Based on arXiv:1810.11463 and arXiv:1912.02468 in collaboration with A. Gimenez Grau, C. Kristjansen, M. Wilhelm. (click to hide)
Tue
01.12.
16:00
zoom: 940 4378 1498
Xinan Zhou (Princeton)
“All holographic four-point correlators in maximally supersymmetric CFTs”
abstract (click to view) Holographic correlators are natural objects to test and exploit the AdS/CFT correspondence. However, brute force calculations are notoriously difficult and have led to only a handful results in the past two decades. In this talk, I will introduce a powerful new method to constructively derive all tree-level four-point functions in holographic CFTs with maximal supersymmetry. I will introduce the notion of maximally R-symmetry violating (MRV) limit, which is key to our construction. In this limit, the correlators simplify drastically and become easy to compute. I will then show that the full correlators can be reconstructed from the MRV limit by using symmetries. A remarkable feature is that the four-point functions do not have intrinsic contact interactions, and can be expressed as sums of exchanges alone. Using this method we reproduce the known results for AdS5xS5 dual to 4d N=4 SYM, and also compute all four-point functions from AdS4xS7 and AdS7xS4, dual respectively to 3d N=8 ABJM and the 6d (2,0) theory. The amplitudes for these different theories exhibit a surprising universality. (click to hide)
Tue
08.12.
16:00
zoom: 940 4378 1498
Fabrizio Nieri (DESY)
“ε-deformed W algebras: 4d N=2 gauge theories, 2d CFT and (bi)spectral duality”
abstract (click to view) I will present a constructive definition of ε-deformed or Yangian version of q-W algebras which feature in the brane engineering of 5d N=1 quiver gauge theories. This new type of algebras fill in the missing intermediate level between q-deformed and un-deformed W algebras, and I will explain in which sense the ε-deformed algebras are (bi)spectral duals to the ordinary ones. In particular, I will discuss how the ε-deformed conformal blocks manifestly reproduce instanton partition functions of 4d N = 2 quiver gauge theories and give dual (unconventional) integral representations of Toda conformal blocks via AGT duality. Finally, I will also consider an application to integrable many-body systems. (click to hide)
Tue
15.12.
16:00
zoom: 940 4378 1498
Owen Gwilliam (Massachusetts, Amherst)
“Holomorphic field theories and factorization algebras”
abstract (click to view) Field theories whose equations of motion are holomorphic in nature have intrinsic appeal to mathematicians, but they also arise naturally as twists of supersymmetric theories. I will describe a few examples and how they lead to higher-dimensional analogs of well-known results in 2d chiral conformal field theory, by using a combination of the Batalin-Vilkovisky formalism and the language of factorization algebras. No background in BV or factorization algebras is required; I'll introduce what is needed along the way. (click to hide)

last modified: Tue, 8 Dec 2020, 12:52 CET