Abstract
In large-Nc 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.
Highlights
Applicability of hydrodynamics to the infrared (IR) dynamics of various systems without quasiparticles has been firmly established much more recently through the advent of gaugegravity duality [25,26,27,28]
With a view towards a better understanding of heavy ion collisions, the goal of this program has been to uncover qualitative and quantitative features of physical phenomena across a wide range of coupling constants — an understanding of which will likely require an interpolation between weakly-coupled perturbative field theory and strongly-coupled holographic techniques
We studied the gravity backgrounds dual to a boost-invariant Bjorken flow, which are good models for the late time dynamics of heavy ion collisions, at least in the regime of mid-rapidities
Summary
We begin by expressing the equations that describe the boost-invariant evolution of chargeneutral, conformal relativistic fluids, which will be studied in this work. What remains is for us to find the solution for the additional scalar degree of freedom that is required to fully characterize the flow In this case, it is convenient to work with a proper time-dependent energy density ε(τ ) and write eq (2.1) as in [98]: Dε + (ε + P ) ∇aua + Πab∇aub = 0. The Bjorken expansion in proper time formally has a zero radius of convergence [95] This means that at some order, the expansion in inverse powers of τ breaks down and techniques of resurgence are required for analyzing long-distance transport This means that at some order, the expansion in inverse powers of τ breaks down and techniques of resurgence are required for analyzing long-distance transport (see e.g. [95, 107,108,109,110,111,112])
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