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Speakers: Blaise Gouteraux (Ecole Polytechnique, Paris) and Fridrik Freyr Gautason (KU Leuven). Location: Utrecht, Unnik building 220.

Date 30 November 2018 13:00 -18:00

## Programme

13:30 Tea & Coffee

14:00 Blaise Gauteroux (Ecole Polytechnique, Paris)Slow relaxation and diffusion in holography

15:15 Coffee break

15:45 Fridrik Freyr Gautason (KU Leuven)The three twists of N = 4 and holography

17:00 Borrel (drinks and snacks) The Basket, Genevelaan 8, 3584 CC Utrecht (next to Unnik-building)

## Abstracts

Blaise Gauteroux (Ecole Polytechnique, Paris)Slow relaxation and diffusion in holography

Abstract: The dissipative dynamics of strongly interacting systems are often characterised by the timescale set by the inverse temperature $\tau_P\sim\hbar/(k_BT)$. So are the dynamics near black hole horizons. I will explain how this statement needs to be amended in the presence of weakly broken symmetries, and/or near quantum critical points in the presence of a dangerously irrelevant deformation. In both cases, there is a collective excitation (a quasinormal mode of the dual black hole spacetime) whose lifetime $\tau_{eq}$ is parametrically longer than $\tau_P$: $\tau_{eq}\gg T^{-1}$. This generally leads to anomalously large diffusivities (in units of the butterfly velocity), governed by $\tau_{eq}$ rather than $\tau_P$. The existence of this long-lived excitation also means that the system equilibrates slowly on timescales much longer than $\tau_P$.

Fridrik Freyr Gautason (KU Leuven)The three twists of N = 4 and holography

Abstract: I will start by reviewing the three inequivalent topological twists of N = 4 SYM on arbitrary four-manifolds and briefly discuss the resulting topological QFTs. I will emphasise the role played by global anomalies of N = 4 in our story and the relation to anomalies in the TQFTs. I will then construct type IIB supergravity solutions that are holographic duals to the aforementioned twists.

## Location

Willem C. van Unnikgebouw ('Unnik'), room 220, Heidelberglaan 2, Utrecht >>GoogleMaps

Local organiser

Umut Gursoy (UU)