Phenomenology of Irreversible Processes from Gravity

TL;DR

This paper develops a phenomenological framework for modeling the evolution of strongly coupled matter in heavy ion collisions, linking it to gravity via AdS/CFT correspondence to describe non-equilibrium dynamics and transition to hydrodynamics.

Contribution

It introduces a unified set of phenomenological equations derived from AdS/CFT that describe the entire evolution from non-equilibrium to hydrodynamic behavior in heavy ion collisions.

Findings

Equations accurately describe late-stage equilibration.

Solutions correspond to regular gravity horizons in AdS.

Framework bridges field theory and gravity descriptions.

Abstract

We propose that the space-time evolution of strongly coupled matter formed by ultra-relativistic heavy ion collisions can be modelled by phenomenological equations involving the energy-momentum tensor and conserved currents alone. These equations can describe the late stage of local chemical and thermal equilibration of the matter formed after collisions, and its subsequent transition to hydrodynamic expansion in an unified framework. The full set of equations include local energy, momentum and charge conservation; but also additional equations for evolution of non-equilibrium variables. These equations with precisely determined phenomenological parameters can be obtained by the AdS/CFT correspondence. On the gravity side of this correspondence, for vanishing chemical potentials, these phenomenological equations give all solutions of pure gravity in AdS which have regular future horizons. We also discuss field-theoretic grounds for validity of these phenomenological equations.