“Strings, CFT & Integrability”
Fall Semester 2015
Organised by: Niklas Beisert, Matthias Gaberdiel and Christoph Keller
day
date
date
time
venue
venue
speaker
title
title
Wed
30.09.
11:30
HIT E41.1
Alessandro Sfondrini (ETH Zürich)
“Integrability for AdS3/CFT2”
Wed
14.10.
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.
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.
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.
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)
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)
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)
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)
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