Talk Titles and Abstracts

Tomas Andrade - Commensurate lock-in in holographic non-homogeneous lattices

We will consider the spontaneous formation of striped structures in a holographic model which possesses explicit translational symmetry breaking, dual to an ionic lattice with spatially modulated chemical potential. By studying the marginal modes which drive the transition to the stripped phase, we will discover that there is a commensurate lock-in between the spontaneous stripes and the underlying ionic lattice, which takes place when the amplitude of the lattice is large enough. We will also discuss some non-linear solutions which we expect to be the end points of such instabilities.

Glenn Barnich - BMS current algebra & field dependent central extension

The BMS current algebra in four-dimensional asymptotically flat spacetimes at null infinity that generalizes the Bondi mass loss formula is discussed. Different formulations of the associated field-dependent central extension are also presented.

Nikolay Bobev - RG Flows Across Dimensions and Holography

Superconformal field theories placed in nontrivial background fields for the metric and the continuous global symmetries exhibit a rich web of RG flows across dimensions. I will discuss several examples of such flows and emphasize some of their universal features. In addition, I will employ non-perturbative tools such as 't Hooft anomaly matching, a-, F-, and c-extremization, and holography to gain a quantitative understanding of some aspects of these theories. Finally, I will discuss the relevance of these results for a microscopic understanding of the entropy of supersymmetric black holes and strings in AdS.

Aristomenis Donos - Black Holes, Stokes Flows, and Transport at Strong Coupling

Remarkable advancements in condensed matter physics have revealed a plethora of novel transport phenomena occurring in strongly coupled phases of matter. To understand them, an intrinsically non-perturbative treatment of Quantum Field Theory is necessary. Holography provides a natural framework to examine the transport properties of strongly coupled systems from first principles. I will discuss how black holes horizons provide an auxiliary fluid description of transport at low frequencies

Roberto Emparan - The singularity is near

I will discuss ongoing work with Umpei Miyamoto and Jorge Rocha to understand the violation of cosmic censorship in the evolution and break up of black strings.

Mirah Gary - The BMS Bootstrap

Field theories with BMS symmetry arise in a number of contexts, including as the holographic duals of asymptotically flat spacetimes, the worldsheet dynamics of tensionless strings, and as RG fixed points of non-relativistic field theories. We examine two-dimensional field theories with BMS3 symmetry and, using highest weight representations, construct the BMS bootstrap equation by formulating the notion of crossing symmetry in the four-point functions of these field theories. In the limit of large central charges, we find analytic expressions for the BMS blocks that are the basic ingredients for the solution of the bootstrap equation. This constitutes the first example of the formulation and solution of a bootstrap equation in a theory which is not a relativistic conformal field theory.

Troels Harmark - Spin Matrix theory limits of the AdS/CFT correspondence

One of the challenges in using the AdS/CFT correspondence to study quantitatively how space, time and gravity emerges from a quantum theory is that one does not know in general how to interpolate between the two sides of the duality. In the planar limit with infinite N, an integrable spin chain has been found that can provide a quantitative unifying framework enabling an interpolation between planar gauge theory and tree-level string theory. Can one do something like this also for finite N where gravity and black holes are part of the game? We propose another kind of limit of the AdS/CFT correspondence in which one gets a type of quantum mechanical theory called Spin Matrix theory that generalizes spin chains to finite N. We review that in the limit giving SU(2) Spin Matrix theory, one can use it to interpolate between the gauge theory and string theory sides both for tree-level string theory and for interacting D-branes (Giant Gravitons). Moreover, we show that the Spin Matrix theory limits of string theory on AdS5 x S5 result in non-relativistic strings moving in a certain type of non-relativistic geometry.

Nabil Iqbal - Generalized global symmetries, dissipative magnetohydrodynamics, and holography

Just as ordinary global symmetries in quantum field theory are associated with conserved currents that count particle numbers, “generalized” global symmetries are associated with higher-form conserved currents that can be understood as counting higher-dimensional objects such as strings. I will discuss how this idea applies to the long-distance structure of theories of electromagnetism, where a key role is played by a higher-form conserved current that counts the density of magnetic flux lines. I will then use this higher form current to reformulate dissipative magnetohydrodynamics from the point of view of generalized symmetries and effective field theory. I will also briefly discuss the structure of the holographic dual to magnetohydrodynamics, which involves a two-form field propagating in the bulk.

David Mateos - X-treme Holography

I will discuss application of the gauge/string duality to QCD in extreme conditions.

Niels Obers - Hydrodynamics for systems with and without boost symmetries

System that are characterized by a dynamical scaling exponent z>1 can have Galilean (non-relativistic) or Carrollian (ultra-relativistic) boost invariance, but generically have no boost symmetries at all. In this talk I will discuss how to describe such theories in the hydrodynamic limit. I will start by discussing an ideal gas of Lifshitz particles and subsequently describe the general thermodynamic properties of systems with no boost symmetries by introducing velocity as a chemical potential whose conjugate variable is momentum. This can be used to give a general description of perfect fluids with no presupposed knowledge of its boost symmetries if any. Results on first order corrections will also be discussed. Finally, I will present a holographic setup involving boosted black LIfshitz branes which provides a realization of the non-boost invariant hydrodynamics at the perfect fluid level.

Simon Ross - Entanglement shadows in LLM geometries

Entanglement shadows are regions of spacetime which Ryu-Takayanagi surfaces do not enter, providing an obstruction to the reconstruction of the geometry from the minimal surfaces. I will present a new example in the LLM geometries, which is also related to work on entanglement on the S^5 factor.

Jorge Santos - Violating weak cosmic censorship in AdS4

We consider time-dependent solutions of the Einstein-Maxwell equations using anti-de Sitter (AdS) boundary conditions, and provide the first counterexample to the weak cosmic censorship conjecture in four spacetime dimensions. Our counterexample is entirely formulated in the Poincare patch of AdS. We claim that our results have important consequences for quantum gravity, most notably to the weak gravity conjecture.

Ulrich Sperhake - Black-hole collisions in higher-dimensional general relativity

The collision of two black holes in higher dimensions offers a

unique channel to probe D dimensional general relativity in its most

extreme non-linear and strong-field regime. It facilitates investigation

of the cosmic censorship and hoop conjectures, offers a way to model heavy

ion collisions through the gauge gravity duality and informs us about the

loss of energy-momentum in high-energy collisions performed to probe

so-called TeV gravity scenarios. Motiovated in particular by the latter,

we summarize our (rather comprehensive) understanding of high-energy

collisions of black holes in four dimensions and present ongoing work on

the gravitational wave emission in black hole collisions in higher

dimensional spacetimes either starting from rest or with initial boosts up

to about 70% of the speed of light.

Benson Way - Precision Holography with Localised Black Holes

I discuss two instances where the Gregory-Laflamme instability and its

associated phase transition has an explicit field theory dual. One case

is in type IIB SUGRA on $AdS_5\times S^5$ where the transition is dual

to R-symmetry breaking in $\mathcal N=4$ supersymmetric Yang-Mills, and

the other is in IIA SUGRA where the transition is dual to a

confinement/deconfinement transition in maximally supersymmetric

Yang-Mills in (1+1)-dimensions. We compute the location of the

first-order phase transitions within these theories on the gravity side

and in the latter case make comparisons with available lattice results.