Stability of Initial Glasma Fields

TL;DR

This paper performs a linear stability analysis of the initial gluon fields, called glasma, in relativistic heavy-ion collisions, revealing the instability of chromomagnetic fields and deriving their growth rates, with implications for early collision dynamics.

Contribution

It provides a theoretical stability analysis of glasma fields assuming uniformity and SU(2) gauge symmetry, highlighting the instability of chromomagnetic fields and comparing with numerical simulations.

Findings

Chromomagnetic fields are unstable in the glasma.

Growth rates of unstable modes are derived.

Results are compared with plasma instability simulations.

Abstract

A system of gluon fields produced in the earliest phase of relativistic heavy-ion collisions, which is called `glasma', can be described in terms of classical fields. Initially there are chromoelectric and chromomagnetic fields along the collision axis. A linear stability analysis of these fields is performed, assuming that the fields are space-time uniform and using the SU(2) gauge group. We apply Milne coordinates and the gauge condition which are usually used in studies of glasma. The chromoelectric field is in the Abelian configuration with the corresponding potential linearly depending on coordinates but the chromomagnetic field is in the nonAbelian configuration generated by the potential of non-commuting components. The chromomagnetic field is found to be unstable and the growth rate of the unstable mode is derived. Our findings are critically debated and confronted with the numerical simulations by Romatschke and Venugopalan who found that the evolving glasma is unstable due to the Weibel instability well-known in electromagnetic plasma.