Holographic constraints on Bjorken hydrodynamics at finite coupling

TL;DR

This paper investigates how finite coupling corrections in holographic models affect the dynamics of Bjorken hydrodynamics, analyzing non-local observables and the validity of hydrodynamics at early times in heavy-ion collisions.

Contribution

It introduces a study of finite coupling effects on Bjorken flow using supergravity models, providing analytical insights into hydrodynamization and the applicability of hydrodynamics.

Findings

Hydrodynamics convergence improves to third order in the expansion.

Applicability of hydrodynamics is delayed at weaker couplings.

Non-local observables can be expressed in terms of a few parameters.

Abstract

In large-$N_c$ conformal field theories with classical holographic duals, inverse coupling constant corrections are obtained by considering higher-derivative terms in the corresponding gravity theory. In this work, we use type IIB supergravity and bottom-up Gauss-Bonnet gravity to study the dynamics of boost-invariant Bjorken hydrodynamics at finite coupling. We analyze the time-dependent decay properties of non-local observables (scalar two-point functions and Wilson loops) probing the different models of Bjorken flow and show that they can be expressed generically in terms of a few field theory parameters. In addition, our computations provide an analytically quantifiable probe of the coupling-dependent validity of hydrodynamics at early times in a simple model of heavy-ion collisions, which is an observable closely analogous to the hydrodynamization time of a quark-gluon plasma. We find that to third order in the hydrodynamic expansion, the convergence of hydrodynamics is improved and that generically, as expected from field theory considerations and recent holographic results, the applicability of hydrodynamics is delayed as the field theory coupling decreases.