Sebastian Waeber

We consider hairy, magnetic black brane solutions to Einstein-Maxwell-Chern-Simons-Dilaton theory with full backreaction of the scalar and gauge fields and compute the time evolution with time dependent sources. The dual field theory’s ’t Hooft anomaly leads to long-lived current oscillations in the low temperature limit long after the electric pulse which created these modes has been switched off. We find that, generally, nonlinear effects increase the decay rates of long-lived modes by a temperature dependent amount. Nonetheless, our results suggest that the lifetime of time-translation symmetry breaking states can be made arbitrarily large if the temperature after the quench is sufficiently small. Experimentally this might be realizable in Weyl semimetals.

We consider magnetically charged AdS black branes with vanishing entropy at zero temperature. We argue that in the presence of a large enough Chern-Simons coupling the quasi normal modes of the brane will have a diminishing imaginary part. Since our result is agnostic to the matter content of the theory it implies that, generically, the boundary theory will possess long lived modes which should be observable in a proper setting.

A bstract: We study the turbulent dynamics of a relativistic (2 + 1)-dimensional fluid placed in a stochastic gravitational potential. We demonstrate that the dynamics of the fluid can be obtained using a dual holographic description realized by an asymptotically Anti-de Sitter black brane driven by a random boundary metric. Using the holographic duality we study the energy power spectrum of a fluid with an inverse energy cascade and show that it is compatible with that of a compressible fluid flow. We calculate the local energy dissipation and the local fluid velocity distribution which provide other measures of the holographic fluid turbulence.

We discuss analytic solutions describing magnetically charged black branes in d dimensional AdS space. Focusing on d = 5, we study the response of the brane to an external short lived electric field. We argue that when the theory possesses an ’t Hooft anomaly then at sufficiently low temperature a long lived oscillatory current will be observed long after the electric field has been turned off. We demonstrate this “anomalous resonance” effect via a numerical study.

We study the turbulent dynamics of a relativistic (2 + 1)-dimensional fluid placed in a stochastic gravitational potential. We demonstrate that the dynamics of the fluid can be obtained using a dual holographic description realized by an asymptotically Anti-de Sitter black brane driven by a random boundary metric. Using the holographic duality we study the inverse cascade energy power spectrum of the fluid and show that it is compatible with that of a compressible fluid flow. We calculate the local energy dissipation and the local fluid velocity distribution which provide other measures of the holographic fluid turbulence.

We apply a recent and simple technique which speeds up the calculation of localized collisions in holography to study more realistic models of heavy ion collisions via the gauge/gravity duality. The initial data takes into account the lumpy nuclear structure of real heavy ions and the projectiles' aspect ratio mimics the Lorentz contraction of nuclei during RHIC collisions. At the hydrodynamization time of the central region of the quark gluon plasma developed during the collision, we find that most of the vorticity three vector's absolute value is deposited far away from the hydrodynamized part of the plasma. Only the relativistic corrections to the thermal vorticity in the hydrodynamized region are non-negligible. We compare the transverse flow after the collision determined in this work with previous results, without granular initial conditions and determine the proper energy density and fluid velocity in a hydrodynamized subregion of the plasma.

We study the ensemble average of the thermal expectation value of an energy momentum tensor in the presence of a random external metric. In a holographic setup this quantity can be read off of the near boundary behavior of the metric in a stochastic theory of gravity. By numerically solving the associated Einstein equations and mapping the result to the dual boundary theory, we find that the non relativistic energy power spectrum exhibits a power law behavior as expected by the theory of Kolmogorov.