25-29 April 2016
Niels Bohr Insitute
Europe/Copenhagen timezone

Poster session

During the week of the Workshop and in particular during the reception there will be a poster session. 

Mahdis Ghodrati
Title: "Schwinger effect and entanglement entropy in confining geometries"
Abstract: By using AdS/CFT, we study the critical electric fields, Schwinger pair creation rates, potential phase diagrams for the quark and anti quark and entanglement entropies of a strip in four confining supergravity solutions which are Witten QCD, Maldacena-Nunez, Klebanov-Tseytlin and Klebanov-Strassler models and then we compare them with each other which the results could be used in measuring entanglement entropy. We find that the phase transitions have higher rate in WQCD and KT relative to MN and KS. We also find that increasing the parallel magnetic field relative to electric field would increase the pair creation rate and increasing the perpendicular magnetic field would decrease the rate. 

Nina Miekley
Title: "Non-local observables at finite temperature in AdS/CFT"
Abstract: We examine non-local observables in finite temperature field theories dual to SUGRA on Schwarzschild-AdS spacetime in arbitrary dimension. We compute the equal-time two-point function, the spatial Wilson loop and the entanglement entropy for a strip, which are observables determined by the area of bulk extremal surfaces. The results can be expressed in terms of generalised hypergeometric functions, expanding on previous results. Furthermore, we compare how far these field theory observables probe the bulk spacetime, showing that extremal surfaces with higher dimension reach deeper into the bulk.

Ioannis Papadimitriou
Title: "Thermodynamics, transport and relaxation in non-conformal theories"
Abstract: We study the equilibrium and near-equilibrium properties of a holographic five-dimensional model consisting of Einstein gravity coupled to a scalar field with a non-trivial potential. The dual four-dimensional gauge theory is not conformal and, at zero temperature, exhibits a renormalisation group flow between two different fixed points. We quantify the deviations from conformality both in terms of thermodynamic observables and in terms of the bulk viscosity of the theory. By computing the quasi-normal modes of the system we identify two different relaxation channels. At high temperatures, the system first isotropises, meaning that all pressures become equal, and subsequently equilibrates, meaning that the equation of state becomes applicable. At low temperatures the order of these two processes is reversed.
 
Nick Poovuttikul
Title: "Toward hydrodynamics-like theory without translational symmetry"
Abstract: We propose a consistent way to construct an effective theory of a hydrodynamics-like systems without translational symmetry. The procedure can be done by modify the reconstruct the constitutive relation from thermodynamics quantities, fluid velocity and scalar fields, which break the translational symmetry explicitly. We identify the shear viscosity from the coefficient of the shear tensor in the modified constitutive relation and show that such coefficient deviate from the one obtained by the usual Kubo formula even at the leading order in momentum relaxation scale. The universal bound and its relation with the entropy production rate in this hydrodynamic-like theory are also discussed. 

Marco Sanchioni
Title: "Gravitational Tension, Spacetime Pressure and Black Hole Volume"
Abstract: We study the first law of black hole thermodynamics in the presence of surrounding gravitational fields and argue that variations of these fields are naturally incorporated in the first law by defining gravitational tension or gravitational binding energy. We demonstrate that this notion can also be applied in Anti-de Sitter spacetime, in which the surrounding gravitational field is sourced by a cosmological fluid, therefore showing that spacetime volume and gravitational tension encode the same physics as spacetime pressure and black hole volume. We furthermore show that it is possible to introduce a definition of spacetime pressure and black hole volume for any space time with characteristic length scales which does not necessarily require a cosmological constant sourcing Einstein equations. However, we show that black hole volume is non-universal in the flat spacetime limit, questioning its significance. We illustrate these ideas by studying the resulting black hole volume of Kaluza-Klein black holes and of a toy model for a black hole binary system in five spacetime dimensions (the black saturn solution) as well as of several novel perturbative black hole solutions. These include the higher-dimensional Kerr-Newman solution in Anti-de Sitter spacetime as well as other black holes in plane wave and Lifshitz spacetimes
 
Watse Sybesma
Title: "Holographic Equilibration of Nonrelativistic Plasmas"
Abstract: We study far-from-equilibrium physics of strongly interacting plasmas at criticality and zero charge density for a wide range of dynamical scaling exponents z in d dimensions using holographic methods. In particular, we consider homogeneous isotropization of asymptotically Lifshitz black branes with full backreaction. We find stable evolution and equilibration times that exhibit small dependence of z and are of the order of the inverse temperature. Performing a quasinormal mode analysis we find a corresponding narrow range of relaxation times, fully characterized by the fraction z/(d-1). For z>=d-1, equilibration is overdamped, whereas for z<d-1 we find oscillatory behavior. This poster is based on arXiv 1602.01375.