String theory implications on causal hydrodynamics

TL;DR

This work investigates how string theory via the AdS/CFT correspondence informs causal hydrodynamics for quark-gluon plasma by extracting relaxation times and dispersion relations in holographic plasmas. It finds that the Israel-Stewart picture is not universally valid across gauge theories and that higher-order (third-order) contributions can be significant, particularly in certain channels, though eta/s remains near the universal strong-coupling value. The relaxation time tau_pi varies across theories (not universal) and is typically around 0.2 fm, with the front propagation speed v_front often close to the sound speed v_s; the ratio tau_pi/eta shows limited coupling dependence. These results provide practical guidance for QGP modeling and highlight limitations of the Israel-Stewart framework, while suggesting that strong-coupling insights from string theory can complement kinetic theory in hydrodynamic simulations.

Abstract

We summarize the main lessons for causal hydrodynamics/second order hydrodynamics/Israel-Stewart theory from string theory.

Figures (1)

• Figure 1: When one adds a perturbation to a black hole, the black hole behavior is similar to a hydrodynamic system. In hydrodynamics, this is a consequence of viscosity.