Speaker: Romuald Janik

Title:  Holographic phase transitions in real time

Abstract: In this talk I would like to describe our works on holographic systems with a first order phase transition starting from a linearized analysis and going over to numerical simulations exploring the endpoint of the spinoidal instability. 

 

Speaker: Javier Mas

Title:  Pumping and Driving in Global AdS

Abstract: The most studied boundary conditions of fields in AdS are dual to quenches in the dual field theory. We initiate the study of more general time dependent boundary conditions which are believed to have a correspondence in physics of driven systems that can be devised experimentally. We will report on two classes of boundary conditions: infinitely slow quench and periodic driving. We chart out the space of stable solutions and study the endpoint of unstable modes. The expected black hole solutions is not always such and endpoint and pulsating solutions that resemble relaxation oscillations can appear. 

 

Speaker: Martin Ammon

Title: Condensed matter musings: surface states in holographic Weyl semimetals & transverse gapped phonons

Abstract: The talk consists of two parts. In the first part I discuss the surface states of a strongly coupled Weyl semimetal within holography. By explicit numerical computation of an inhomogeneous holographic Weyl semimetal we will find an an electric current restricted to the surface in presence of electric chemical potential. The total current is universal in the sense that it only depends on the topology of the phases showing that the bulk-boundary correspondence holds even at strong coupling. In the second part of the talk I determine the elastic response of planar black hole solutions in a simple class of holographic models with broken translational invariance. We compute the transverse quasi-normal mode spectrum and determine the propagation speed of the lowest QNM. This speed relates to the rigidity modulus, as dictated by the elasticity theory, and hence the mode may be interpreted as a gapped transverse phonon.

 

 

Speaker: Bin Chen

Title: On the Mutual Information in Conformal Field Theory

Abstract: In this work, we study the universal behaviors in the mutual information of two disjoint spheres in a conformal field theory(CFT). By using the operator product expansion of the spherical twist operator in terms of the conformal family, we show that the large distance expansion of the mutual information can be cast in terms of the conformal blocks. We develop the 1/n prescription to compute the coefficients before the conformal blocks. For a single conformal family, the leading nonvanishing contribution to the mutual information comes from the bilinear operators. We show that the coefficients of these operators take universal forms and such universal behavior persists in the bilinear operators with derivatives as well. Consequently the first few leading order contributions to the mutual information in CFT take universal forms. To illustrate our framework, we discuss the free scalars and free fermions in various dimensions. For the free scalars, we compute the mutual information to the next-to-leading order and find good agreement with the improved numerical lattice result. For the free fermion, we compute the leading order result, which is of universal form, and find the good match with the numerical study. Our formalism could be applied to any CFT potentially.

 

 

Thursday  07-09

 

Speaker: Julian Sonner

Title: Thermalisation of pure states

Abstract: In this talk I will present some recent progress in studying thermalisation in low-dimensional systems with holographic duals. Firstly I will describe first-principles field theory calculations in pure states dual to collapsing black holes, highlighting the role of non-perturbative corrections in the information-loss problem. Secondly, I will show how eigenstate thermalisation supplies a unifying perspective on many aspects of holographic thermalisation, and in particular on the relation between pure states and bulk geometry.

 

Speaker:  Ling-Yan (Janet) Hung

Title: Exploring the Tensor Network and (p-adic) AdS/CFT

Abstract: We will discuss how various aspects of the AdS/CFT correspondence, particularly the p-adic version of the ads/cft can be recovered by studying a tree like tensor network. In particular, we will find quantitative results such as the recovering of the HKLL relation in bulk operator reconstruction and emergence of Witten diagrams in the computation of correlation functions. We will also discuss interpretations of the tensor network in terms of Wilson lines. 

 

Speaker: David Mateos

Title: Extreme Holography

Abstract: A massive experimental effort will be devoted in the coming years to the physics of QCD in extreme conditions, namely at high energy density and/or high baryon density. Understanding this physics, especially out of equilibrium, is an important theoretical challenge. I will discuss how holography can help us address this challenge. Topics covered will include the far-from-equilibrium dynamics near the QCD critical point, quark matter crystals and colour superconducting phases.

 

 

Speaker: Matthias Kaminski

Title:  Chiral transport from holography & hydrodynamics in strong magnetic fields

Abstract:  We compute quasinormal modes (QNMs) of the metric and gauge field perturbations about black branes electrically and magnetically charged in the Einstein-Maxwell-Chern-Simons theory. By the gauge/gravity correspondence, this theory is dual to a particular class of field theories with a chiral anomaly, in a thermal charged plasma state subjected to a constant external magnetic field, B. Complementary to the gravity calculation, we work out the hydrodynamic description of the dual field theory in the presence of a chiral anomaly, and a constant external B. We find good agreement with the weak field hydrodynamics, which can extend beyond the weak B regime into intermediate B regimes. Furthermore, we provide results that can be tested against thermodynamics and hydrodynamics in the strong B regime. We find QNMs exhibiting Landau level behavior, which become long-lived at large B if the anomaly coefficient exceeds a critical magnitude. Chiral transport is analyzed beyond the hydrodynamic approximation for the five (formerly) hydrodynamic modes, including a chiral magnetic wave.

 

Speaker: Richard Davison

Title: Thermal diffusivity and chaos in holographic theories

Abstract: I will describe how the thermal diffusivity in a wide class of holographic systems is related to the parameters that control the spread of quantum chaos. I will explain how this relation arises as a consequence of the fact that the thermal conductivity of these systems depends only on the metric near the horizon of the dual black hole.

 

 

Friday  08-09

 

Speaker: Elias Kiritsis

Title:  Non-relativistic scale invariant theories and their hydrodynamics

 

Speaker:  Manuela Kulaxizi

Title:    Bulk phase shift and Einstein gravity.

Abstract: The bulk phase shift, related to a CFT four-point function, describes two-to-two scattering at fixed impact parameter in the dual AdS spacetime. We describe its properties for a generic CFT and then focus on large N CFTs with classical bulk duals. We compute the bulk phase shift for vector operators using Regge theory. We use causality and unitarity to put bounds on the bulk phase shift. The resulting constraints bound three-point functions of two vector operators and the stress tensor in terms of the gap of the theory. Similar bounds should hold for any spinning operator in a CFT. Holographically this implies that in a classical gravitational theory any non-minimal coupling to the graviton, as well as any other particle with spin greater than or equal to two, is suppressed by the mass of higher spin particles.

 

Speaker: Koenraad Schalm

Title: Holography and Experimental Quantum Matter

Abstract: A number of very recent experiments on strange metals in the cuprates have again highlighted the anomalous behavior of these materials compared to ordinary Fermi-liquid metals. Almost too good to be true, the displayed behavior again shows remarkable similarities with the qualitative predictions from holography. I will briefly review these experiments and these telltale ever so suggestive similarities.