NumHol2016
Numerical Relativity and Holography
27 June  1 July 2016
Santiago de Compostela, Spain
Program
Registration: Sunday 26th from 18:00 to 21:00 and Monday 27th from 8:30am on.
Conference Opening: Monday 27th at 8:45am
Monday 
Tuesday 
Wednesd. 
Thursday 
Friday 


8:45:009:00 
Opening 

9:0010:15 

10:1511:00 

11:0011:30 

11:3012:15 
Murata 
Mateos 

12:1513:00 

13:0015:00 

15:0015:30 
Excursion 

15:3016:00 

16:0016:30 

16:3017:00 

17:0017:30 

17:3018:00 

18:0018:30 
Posters  
20:30 
Welcome 
Banquet 
Detailed Program:
Monday 27/06/2016
8:459:00 
Opening 

chair: Matthias Kaminski 

9:0010:15 
Holzegel, Gustav 
Local and global dynamics in asymptotically AdS spacetimes 
10:1511:00 
Craps, Ben 
AdS (in)stability: an analytic approach and its interplay with numerics 
11:0011:30 
Coffe Break 

11:3012:15 
Murata, Keiju 
Turbulent strings in AdS/CFT 
12:1513:00 
Tian, Yu 
Stability and nonequilibrium physics in holography. 
13:0015:00 
Lunch 

chair: Ben Craps 

15:0015:30 
Triana, Miquel 
Holographic heavy ion collisions with baryon charge 
15:3016:00 
Jansen, Aron 
Holographic Thermalization in Nonrelativistic Plasmas 
16:0016:30 
Coffe Break 

17:0017:30 
Wu, Jackson 
Quantum quench in a holographic model of the Kondo effect 
16:3017:00 
Panosso Macedo, Rodrigo 
Phase diagram of 4D field theories with chiral anomaly from holography 
17:3018:00 
Koirala, Roshan 
Quasinormal modes of electric and magnetic branes 


19:0020:30 
Guided Tour 

20:30 
Welcome Cocktail 
Tuesday 28/06/2016
chair: Julian Sonner 

9:0010:15 
Janik, Romuald 
Quasinormal modes: from high order hydrodynamics to nonconformal plasma 
10:1511:00 
Rostworowski, Andrzej 
Current status of AdS instability:. 
11:0011:30 
Coffe Break 

11:3012:15 
Mateos, David 
Towards the string dual of a color superconductor 
12:1513:00 
Ishii, Takaaki 
Holographic correlation functions out of equilibrium 
13:0015:00 
Lunch 

chair: Miguel Costa 

15:0015:30 
Hartmann, Betti 
The influence of the GaussBonnet interaction on the properties of boson stars and hairy black holes 
15:3016:00 
Attems, Maximilian 
Holographic Heavy Ion Collisions in NonConformal Theories 
16:0016:30 
Coffe Break 

16:3017:00 
Pantelidou, Christiana 
Stripes phases in external magnetic field 
17:0017:30 
Kim, Keun Young 
Homes' law in holographic superconductors 
17:3018:00 
Jankowski, Jakub 
Relaxation rates and phase transitions 
18:0018:30 
Posters 
Wednesday 29/06/2016
chair: Michal Spalinski 

9:0010:15 
Yaffe, Laurence 
Collisions, quasiparticles, and confinement dynamics: holographic lessons and puzzles. 
10:1511:00 
Withers, Benjamin 
Quenching an electric field in metallic holography 
11:0011:30 
Coffe Break 

11:3012:15 
Romatschke, Paul 
Simulating YangMills in 9+1 dimensions 
12:1513:00 
Green, Stephen 
Superradiant instabilities of asymptotically AdS black holes 
13:0015:00 
Lunch 

15:00 
Excursion 
Thursday 30/06/2016
chair: Martin Ammon 

9:0010:15 
Donos, Aristomenis 
T.B.A. 
10:1511:00 
Buchel, Alex 
Beyond adiabatic approximation in Big Bang Cosmology: 
11:0011:30 
Coffe Break 

11:3012:15 
Ramallo, Alfonso V. 
Cold holographic matter in topdown models 
12:1513:00 
Zilhao, Miguel 
Holographic Heavy Ion Collisions in Confining Theories 
13:0015:00 
Lunch 

chair: Jonathan P. Shock 

15:0015:30 
Kunesch, Markus 
Black hole instabilities and weak cosmic censorship in higher dimensions 
15:3016:00 
Alsup, James 
Fermions in a spontaneously generated holographic lattice 
16:0016:30 
Coffe Break 

16:3017:00 
Krikun, Alexander 
Fermions in Helical Background 
17:0017:30 
Greenspan, Lauren 
Polarised Black Holes in AdS 
17:3018:00 
Nguyen, Phuc 
Holographic Entanglement Chemistry 



20:30 
Banquet 
Friday 01/07/2016
chair: Pau Figueras 

9:0010:15 
Bantilan, Hans 
Colliding Black Holes in AdS 
10:1511:00 
Van der Schee, Wilke 
Evolution of the jet opening angle distribution in holographic plasma 
11:0011:30 
Coffe Break 

11:3012:15 
Casalderrey Solana, Jorge 
Holographic ThreeJet Events in Strongly Coupled N=4 YangMills Plasma 
12:1513:00 
Andrade, Tomas 
Isotropisation at Finite Coupling 
13:0015:00 
Lunch 

chair: David Mateos 

15:0015:45 
Arean, Daniel 
Holographic Noise 
15:4516:30 
Jiménez, Amadeo 
Time evolution of anomalous currents in holography 
Posters
Biasi, Anxo 
Modelling Gravitational Collapse in AdS with the Nonlinear Schrödinger Equation 
Fernández, Daniel 
Far from equilibrium energy flow and entanglement entropy 
Paredes, Ángel 
A wave interpretation of dark matter to explain galactic offsets 
Ren, Rie 
Analytic anisotropic solutions for holography 
Serantes, Alexandre 
Adiabatic Pumping Solutions in AdS 
Alphabetical list
Name 
Abstract 
Alsup, James 
Fermions in a spontaneously generated holographic lattice. We discuss fermions in a spontaneously generated holographic lattice background. The lattice structure at the boundary is generated by introducing a higherderivative interaction term between a U(1) gauge field and a scalar field. We find a critical temperature at which the lattice forms and analyze the band affects on the Fermi surface due to the lattice. 
Andrade, Tomas 
Isotropisation at Finite Coupling. We determine the leading finite coupling correction to the isotropisation time of strongly coupled N=4 Super YangMills (SYM) plasma. To do so, we study the evolution of small perturbations on top of the farfromequilibrium dynamics associated with an anisotropic deformation of thermal AdS. The perturbations are sourced by the higher curvature corrections to the EinsteinHilbert action, which are dual to finite ‘t Hooft coupling corrections of N=4 SYM. By numerically solving the time evolution of the perturbations, we extract the variation of the isotropisation time of the system with respect to the infinite coupling limit. We also perform an analogous analysis in GaussBonnet gravity. This study constitutes the first analysis of finite coupling corrections to the farfromequilibrium dynamics of strongly coupled gauge theories. 
Arean, Daniel 
Holographic Noise. I will review recent progress in the introduction of disorder in holography. I will consider disordered holographic superconductors, and brane intersections. In the former case interesting phenomena like a disorderinduced phase transition, and the formation of islands of superconductivity, are observed. The latter system can be of relevance to describe graphene near the Dirac point; in this context we will show encouraging results for the conductivity of the system. 
Attems, Maximilian 
Holographic Heavy Ion Collisions in NonConformal Theories. Ever since fast hydrodynamization has been observed in heavy ion collisions at RHIC, attempts to understand this feature of the very early nonequilibrium stage have been made. We use the gauge/string duality to model the evolution of strongly coupled QuarkGluon plasma in a nonconformal gauge theory. The nontrivial equation of state and the presence of a time dependent bulk viscosity change the evolution of planar shockwaves. The effect of this nonconformality shows an increase of the relaxation times of the resulting plasma. 
Bantilan, Hans 
Colliding Black Holes in AdS: The collision of black holes is a classic problem in the strongfield regime of general relativity. In the context of AdS/CFT, this process translates to a statement about the boundary field theory's stress tensor: two compact lumps of energy density approach each other from some initial separation, merge, and relax towards the boundary dual of the final state black hole in the bulk. The main purpose of this talk is to outline the ongoing program to work out the details of this picture, via numerical Cauchy evolution of black hole collisions in AdS. I will begin by motivating this program in terms of the heavyion physics it is intended to clarify, then give an overview of the setup, and the generalized harmonic method we use to solve the Einstein field equations with a negative cosmological constant. As a concrete example of these ideas, I will describe recent work to remove all simplifying symmetries in black hole collision simulations on a Poincare patch of AdS. 
Buchel, Alex 
Unstable horizons and cosmic censorship violation in holography: In holography one encounters horizons which suffer GregoryLaflamme instability. The dynamical end point of the instability is typically a new equilibrium phase with a nonlinear scalar hair condensate outside the black hole horizon. We review holographic setups where symmetric horizons are unstable, and yet, the suitable equilibrium condensate phase does not exist. We dynamically evolve the simplest model in this exotic class, and show that it leads to violation of cosmic censorship. 
Casalderrey Solana, Jorge 
Holographic ThreeJet Events in Strongly Coupled N=4 YangMills Plasma. We numerically evolve classical string configurations with nontrivial transverse dynamics in AdS5Schwarzschild. These strings develop kinklike structures which, via the gauge/gravity duality, can be interpreted as the propagation of hard gluons produced in association with a quarkantiquark pair in a strongly coupled =4 SYM plasma. We observe the appearance of two physically distinct regimes of the inplasma dynamics, depending on whether the medium is able to resolve the transverse structure of the string prior to its total quench. From these studies we extract the medium resolution scale of the strongly coupled SYM plasma, defined as the smallest angular separation between two jets that the medium can resolve. 
Craps, Ben 
AdS (in)stability: an analytic approach and its interplay with numerics. Numerical work suggests that certain scalar perturbations of AdS of arbitrarily small amplitude $\epsilon$ can form black holes in times of order $1/\epsilon^2$, but that noncollapsing initial data also exist. An analytic approach has emerged from the resummation of secular terms in perturbation theory, leading to effective flow equations governing the dynamics up to times of order $1/\epsilon^2$ (unless nonlinearities become too strong before that time). This approach has led to the discovery of selection rules and conservation laws on the relevant timescales. In combination with numerical work, it is also used in attempts to understand better the onset of instability. 
Donos, Aristomenis 
T.B.A. 
Ramallo, Alfonso V. 
Cold holographic matter in topdown models. I will discuss several holographic models of cold matter in terms of Dbrane intersections. We will analyze the different regimes of the collective excitations of these systems as a function of the temperature and, in particular, their zerosound and diffusion modes, with the aim of determining the universal properties of this kind of holographic matter. 
Green, Stephen 
Superradiant instabilities of asymptotically AdS black holes. Asymptotically AdS spacetimes with reflecting boundary conditions represent a natural setting for studying superradiant instabilities of rotating or charged black holes. In the first part of this talk, I prove that all asymptotically AdS black holes with ergoregions in dimension d ≥ 4 are linearly unstable to gravitational perturbations. This proof uses the canonical energy method of Hollands and Wald in a WKB limit. In the second part of the talk, I consider a charged ReissnerNordstromAdS black holewhich is superradiantly unstable to charged scalar field perturbations at the linear leveland study the full *nonlinear* evolution of the instability. In this special case, the instability occurs even for spherically symmetric perturbations, which simplifies the analysis and allows for the use of numerical general relativity simulations. Our results show that nonlinear backreaction causes the black hole to lose charge and mass to the scalar field as the instability proceeds. Eventually, higher scalar field harmonics become nonsuperradiant, and they are reabsorbed into the black hole. The final state is described by a “hairy” black hole, surrounded by a scalar condensate in the fundamental (lowest) mode. I discuss implications of this work on the original problem of the rotating black hole superradiant instability. 
Greenspan, Lauren 
Polarised Black Holes in AdS. I will discuss solutions of EinsteinMaxwell theory with a negative cosmological constant that asymptote to global $AdS_4$ with a dipolar electrostatic potential turned on at infinity. The potential gives rise to two new geometries: an $AdS$ soliton that includes the full backreaction of the electric field on the $AdS$ geometry, and a neutral black hole that is deformed by the electric field. Boundary data such as the charge density and stress tensor, as well as black hole horizon quantities will be presented. The free energies of the black hole and soliton phases give rise to a phase diagram that generalizes the HawkingPage phase transition, with the soliton dominating the low temperature phase and the black hole dominating the high temperature phase. Coupling this geometry to a scalar field allows us to construct the supergravity duals to ABJM theory, providing a nontrivial example of the gauge/gravity duality. 
Hartmann, Betti 
The influence of the GaussBonnet interaction on the properties of boson stars and hairy black holes. The GaussBonnet (GB) term contains the curvature tensors in quadratic order and appears e.g as the first correction to the EinsteinHilbert action in the low energy effective action of certain String Theories. In contrast to other extensions of General Relativity, the addition of the GaussBonnet term does not alter the degrees of freedom  the equations describing the dynamics of the gravitational field remain second order. However, the GaussBonnet contribution leads to a modification of these equations only in spacetime dimensions larger than four. In this talk, I will describe how the properties of solutions to gravityscalar field models change when taking the GaussBonnet term into account. I will discuss globally regular solutions in the form of socalled boson stars as well as black holes which carry scalar hair on their horizon. In all cases, these solutions have to be constructed numerically by solving systems of coupled nonlinear differential equations. 
Holzegel, Gustav 
Local and global dynamics in asymptotically AdS spacetimes. 
Ishii, Takaaki 
Holographic correlation functions out of equilibrium. In applications of holography, it is important to deal with time dependent systems which require to be solved with numerics. In time dependent setups, correlation functions need to be computed in real time formalism. Based on the linear response theory, we introduce a numerical method to compute real time Green's functions holographically in out of equilibrium systems in which temperature changes. The idea is to make use of pulse sources to obtain retarded Green's functions, and we practically realize such computations in holography. As time frequency analysis, time dependent spectral function is obtained from the real time data, and difference in near and non adiabatic changes of the system is studied. We firstly demonstrate our numerical implementation in one of the simplest holographic models, but we also discuss generalization to other systems. 
Janik, Romuald 
Quasinormal modes: from high order hydrodynamics to nonconformal plasma: In this talk I will review the various contexts in which quasinormal modes make their appearance ranging from a kind of `UV completion' of hydrodynamics to much more applied situations where they provide a limitation on the applicability of hydrodynamics or can be used as real additional degrees of freedom relevant away from equilibrium. 
Jankowski, Jakub 
Relaxation rates and phase transitions. Using a bottomup gauge gravity constructions, relaxation rates of strongly coupled field theories are computed. A variety of phase structures are considered, from a crossover up to a first order phase transition. It is established that near the transition the applicability of a hydrodynamic description breaks down at lower momenta than in the conformal case. In the case of the first order phase transition, a spinodal region appears at temperatures for which the speed of sound squared is negative. An estimate of the preferential scale attained by the unstable modes is also given. Additionally we observe a novel diffusive regime for sound modes over a range of wavelengths. 
Jansen, Aron 
Holographic Thermalization in Nonrelativistic Plasmas. Nonrelativistic plasmas can be described holographically as asymptotically Lifshitz black holes. In this talk I will show how the framework of characteristic evolution can be extended to these spacetimes. We study the simplest case of isotropization in a ddimensional homogeneous plasma with dynamical scaling exponent z. 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/(d1). For z>=d1, equilibration is overdamped, whereas for z 
Jiménez, Amadeo 
Time evolution of anomalous currents in holography. We consider the time evolution of the so called Chiral Magnetic Effect and associated features for strongly coupled systems with axial anomaly at finite temperature. Concretely we are interested in dynamically generating axial charge and looking at the real time response of the system in presence of external electromagnetic fields. We accomplish this via holography. This setup requires solving PDE's which we do using pseudospectral methods in space directions and implicit/pseudospectral methods in time direction. 
Kim, Keun Young 
Homes' law in holographic superconductors. Homes’ law is an empirical law for hightemperature and conventional superconductors. The law states that, for various superconductors, there is a "universal" relation between the superfluid density (\rho_s) at near zero temperature and the transition temperature (T_c) multiplied by the electric DC conductivity (\sigma_DC) in a normal state right above the transition temperature T_c. i.e. \rho_s(T=0) = C \sigma DC(T_c)*T_c, where C is a "universal" constant. We study this universal law in holographic superconductor models with momentum relaxation by numerical holography. 
Koirala, Roshan 
Quasinormal modes of electric and magnetic branes. In this presentation I will explain the quasinormal modes of the electric and magnetic branes. Holographically they are dual to the quark gluon plasma system subjected to the external electric and magnetic field. At the end I will show some possible connection to the experimental results from RHIC/LHC. 
Krikun, Alexander 
Fermions in Helical Background. We study the fermion Green function and the density of states in the holographic model with the translation symmetry breaking realized by the Bianchy VII helix. For the fermion propagating along the helical axis the equations of motion reduce to the relatively simple ODEs. We study the evolution of the spectral function while the background is tuned from the metallic all the way to the deep insulating phase. This allows us to get an insight about the nature of the insulating regime. Interestingly, the helix defines a preferred chirality, therefore due to the "spinhelix" interaction the splitting of the fermion spectral function occurs. 
Kunesch, Markus 
Black hole instabilities and weak cosmic censorship in higher dimensions. In this seminar I will present the results of fully nonlinear numerical simulations of black rings and MyersPerry black holes in five and six dimensions. Most importantly, the endpoint of the GregoryLaflamme instability of very thin rings provides the first concrete evidence that the weak cosmic censorship conjecture can be violated in five dimensional asymptotically flat spacetimes. Furthermore, we have discovered a new instability in black rings which stretches the ring without substantially changing its thickness. This instability completely dominates the evolution for rings of intermediate thickness and always leads to the collapse to a black hole of spherical topology. For very thin rings the GregoryLaflamme instability becomes dominant and eventually gives the ring a fractal structure of bulges connected by necks which become ever thinner over time. I will argue that this suggests that very thin black rings break and hence violate weak cosmic censorship. 
Mateos, David 
Towards the string dual of a color superconductor. Certain phases of QCD at finite baryon density exhibit color superconductivity, namely the spontaneous breaking of the gauge group. We present the construction of string duals of strongly coupled gauge theories that exhibit the same phenomenon. 
Murata, Keiju 
Turbulent strings in AdS/CFT. We study nonlinear dynamics of the flux tube between an external quarkantiquark pair in N=4 super YangMills theory using the AdS/CFT duality. In the gravity side, the flux tube is realized by a fundamental string whose endpoints are attached to the AdS boundary. We perturb the endpoints in various ways and numerically compute the time evolution of the nonlinearly oscillating string. As a result, cusps can form on the string, accompanied by weak turbulence and power law behavior in the energy spectrum. We also find that, with sufficiently strong perturbations, the string continues extending and plunges into the Poincare horizon. In the evolution, effective horizons are also dynamically created on the string worldsheet. The quark and antiquark are thus causally disconnected, and the string transitions to two straight strings. 
Nguyen, Phuc 
Holographic entanglement chemistry. We use the IyerWald formalism to derive an extended first law of entanglement that includes variations in the cosmological constant, Newton's constant and in the case of higher derivative theories all the additional couplings of the theory. In Einstein gravity, where the number of degrees of freedom N2 of the dual field theory is a function of Λ and G, our approach allows us to vary N keeping the field theory scale fixed or to vary the field theory scale keeping N fixed. We also derive an extended first law of entanglement for GaussBonnet and Lovelock gravity. 
Panosso, Macedo Rodrigo 
Phase diagram of 4D field theories with chiral anomaly from holography. Within gauge/gravity duality, we study the class of four dimensional CFTs with chiral anomaly described by EinsteinMaxwellChernSimons theory in five dimen sions. In particular we determine the phase diagram at finite temperature, chemical po tential and magnetic field. At high temperatures the solution is given by an electrically and magnetically charged AdS ReissnerNordstroem black brane. For sufficiently large ChernSimons coupling and at sufficiently low temperatures and small magnetic fields, we find a new phase with helical order, breaking translational invariance spontaneously. For the ChernSimons couplings studied, the phase transition is second order with mean field exponents. Since the entropy density vanishes in the limit of zero temperature we are confident that this is the true ground state which is the holographic version of a chiral magnetic spiral. 
Pantelidou, Christiana 
Stripes phases in external magnetic field. 
Romatschke, Paul 
Simulating YangMills in 9+1 dimensions. 
Rostworowski, Andrzej 
Current status of AdS instability. 
Tian, Yu 

Triana, Miquel 
Holographic heavy ion collisions with baryon charge. Shock wave collisions in AdS space have provided compelling holographic toymodels for heavy ion collisions and the evolution of the resulting quarkgluon plasma. The inclusion of an electromagnetic field in the gravitational setup gives raise to a conserved current in the dual gauge theory, which can be used as a toy model for the baryonic charge. In this project we present the first holographic collisions including this conserved current. 
van der Schee, Wilke 
Evolution of the jet opening angle distribution in holographic plasma. Jets are particularly interesting probes to study the formation and evolution of quarkgluon plasma, as created in heavy ion collisions. In this talk I will briefly review attempts to describe the jet evolution in holography, and will argue that essential progress can be made by studying also the substructure of the jet, such as the evolution of the opening angle. Paying particular attention to the numerics involved, I will illustrate this evolution in a simple holographic model, where we start with energy and angular distributions from pQCD. We identify two competing effects: (1) all individual jets become wider, and (2) the distribution of final jets becomes narrower, since narrow jets suffer less energy loss and are thereby more likely to survive. Both effects can be visible in experimental data. 
Withers, Benjamin 
Quenching an electric field in metallic holography. Recently there has been some interest in the transport properties of holographic models with explicitly sourced inhomogeneities. In these models momentum is not conserved and relaxes to zero exponentially fast in the laboratory frame. I will present the results of an electric field quench in one such model of momentum relaxation at nonzero charge density. I will discuss the nonlinear DC conductivity by quenching to a constant electric field, where in general Joule heating is significant. I will also detail the relaxation back to equilibrium after the electric field is turned off, as governed by a set of vector QNMs. This QNM spectrum depends on a parameter controlling the strength of inhomogeneity which, when dialled to an incoherent regime, encodes a qualitative change in the relaxation of the heat current. 
Wu, Jackson 
Quantum quench in a holographic model of the Kondo effect. We study the dynamics of quantum quench in Kondo systems using gaugegravity duality through a holographic Kondo model. 
Yaffe, Laurence 
Collisions, quasiparticles, and confinement dynamics: holographic lessons and puzzles. The advent of holography has enabled much progress in understanding dynamics in strongly coupled gauge theories. This talk will highlight several questions and puzzles involving collisions of localized shocks resembling heavy ion collisions, quasiparticles in strongly coupled theories, and confinement dynamics in the large N limit. . 
Zilhao, Miguel 
Holographic Heavy Ion Collisions in Confining Theories. Understanding the dynamics of outofequilibrium matter in strongly coupled systems is an important and challenging problem in theoretical physics. A particularly interesting example is the QuarkGluon Plasma formed in relativistic colliders such as RHIC or the LHC, which motivates the study of the relaxation process in strongly coupled nonabelian field theories. An interesting question in this vein is how the presence of a confinement scale affects the relaxation process of such strongly coupled gauge theories. We use holography to map the thermalisation of a confining model to a gravitational system, namely an AdSsoliton model, and study the effect of confinement in the evolution of the system. 