Hydrodynamic fluctuations and long-time tails in a fluid on an anisotropic background

Abstract

The effective low-energy late-time description of many body systems near thermal equilibrium provided by classical hydrodynamics in terms of dissipative transport phenomena receives important corrections once the effects of stochastic fluctuations are taken into account. One such physical effect is the occurrence of long-time power law tails in correlation functions of conserved currents. In the hydrodynamic regime k → 0 this amounts to non-analytic dependence of the correlation functions on the frequency ω. In this article, we consider a relativistic fluid with a conserved global U (1) charge in the presence of a strong background magnetic field, and compute the long-time tails in correlation functions of the stress tensor. The presence of the magnetic field renders the system anisotropic. In the absence of the magnetic field, there are three out-of-equilibrium transport parameters that arise at the first order in the hydrodynamic derivative expansion, all of which are dissipative. In the presence of a background magnetic field, there are ten independent out-of-equilibrium transport parameters at the first order, three of which are non-dissipative and the rest are dissipative. We provide the most general linearized equations about a given state of thermal equilibrium involving the various transport parameters in the presence of a magnetic field, and use them to compute the long-time tails for the fluid.

Second order equilibrium transport in strongly coupled $\mathcal{N} = 4$ supersymmetric $SU(N_c)$ Yang-Mills plasma via holography

“…Needless to say, there is a very rich spectrum of physical effects that arise as a consequence of these out of equilibrium fluctuations, and the second order equilibrium transport properties discussed here will receive important corrections due to the fluctuation effects. Large magnetic fields are also produced during heavy ion collisions [55][56][57] making the background anisotropic, and their presence can also significantly affect the transport and relaxation phenomena occurring in the quark-gluon plasma [46,50,58,59]. Yet another interesting direction to explore would be the effects of the chiral anomaly and the ensuing anomalous transport phenomena.…”

Long-time tails in the SYK chain from the effective field theory with a large number of derivatives

“…As is well known from stochastic [55][56][57][58] and EFT [15] studies, the derivative expansion breaks down due to the hydrodynamic fluctuations, and the long-time tails. However, all these studies are based on the consideration of the first order derivative expansion 4 .…”