Week 21.10.2017 – 29.10.2017


Large Conformal Goldstone Mode Fluctuations in the SYK Model

Regular Seminar Alexander Altland (Koeln)

15:00 City U.
room C310

This talk addresses the low energy physics of the Sachdev-Ye-Kitaev model, a paradigm of strongly interacting (Majorana) quantum matter. A salient feature of this system is its exceptionally high degree of symmetry under reparameterizations of physical time. At low energies this symmetry is spontaneously broken and the ensuing infinite dimensional Goldstone mode manifold takes strong influence on all physical observables. We will discuss the effects of these fluctuations on the example of the so-called out of time ordered correlation functions, diagnostic tools to describe both manifestations of quantum chaos in the system and its conjectured duality to an AdS2 gravitational bulk. While previous work predicts exponential decay of these correlations in time our main finding is that at large time scales non-perturbative Goldstone mode fluctuations generate a crossover to power law behavior. This phenomenon must have ramifications in the physics of the holographic bulk which, however, we do not understand at present.


Chiral Algebras for four dimensional N=4 SCFT

Regular Seminar Carlo Meneghelli (Oxford)

13:15 KCL
room K4.31

Any four dimensional N=2 superconformal field theory (SCFT) contains a subsector of local operator which is isomorphic to a two dimensional chiral algebra. If the 4d theory possesses N=3 or N= 4 superconformal symmetry, the corresponding chiral algebra is an extension the N=2 or (small) N=4 super-Virasoro algebra respectively. In this talk I will present some results on the classification of N=4 chiral algebras and discuss if they can correspond to a 4d theory.

Current Algebra and CFTs at Null Infinity from Amplitudes

Regular Seminar Dhritiman Nandan (Edinburgh)

14:00 IC
room H503

We describe the leading and sub-leading multi-soft behavior of tree level gluon amplitudes and an underlying two-dimensional description of such scenarios where the soft limits are currents related to asymptotic symmetries of YM theory. Such kinematic limits allow us to explore the algebra of these two dimensional currents and we comment on their CFT interpretation. Then we explore a possible two-dimensional description of certain amplitudes in massive scalar QFT’s.


King's Journal Club

Journal Club Rajesh Gupta (KCL)

16:00 KCL
room S4.23

We will discuss "From 3d duality to 2d duality" https://arxiv.org/abs/1710.00926 by Aharony, Razamat and Willett.