# “Strings, CFT & Integrability”

## Fall Semester 2016

Organised by: Niklas Beisert, Matthias Gaberdiel and Christoph Keller

day

date

date

time

venue

venue

speaker

title

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.

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)

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.

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.

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.

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)

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