Stability of Initial Glasma Fields

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.