Early time behavior of spatial and momentum anisotropies in a kinetic approach to nuclear collisions

TL;DR

This paper derives a formula for the early evolution of phase space distributions in nuclear collisions, revealing universal scaling behaviors of anisotropic flow coefficients that differ from fluid dynamics predictions.

Contribution

It provides a general early-time formula for kinetic evolution and shows universal scaling of anisotropic flow coefficients independent of collision details.

Findings

Early-time anisotropic flow scales universally

Scaling behavior differs from fluid dynamics

Derived a general kinetic formula for phase space evolution

Abstract

We derive a general formula for the early time dependence of a phase space distribution evolving according to the kinetic Boltzmann equation. Assuming that the early evolution of the system created in high-energy nuclear collisions can be described by kinetic theory, we calculate the scaling behaviors for the onset of various characteristics of the transverse dynamics. In particular, we show that the scaling behavior of the anisotropic flow coefficients $v_n$ at early times does not depend on the details of the collision kernel or the system composition, while at the same time it differs from the prediction of fluid dynamics.