Instabilities of Initial Gauge Field Configurations in Heavy Ion Collisions

The color-glass-condensate effective theory predicts that strong longitudinal chromo-electric and magnetic fields are generated in the initial stage of high-energy nuclear collisions. We investigate analytically time-evolution of such unique gauge field configurations, and point out that unstable fluctuations are inherent to the longitudinal chromomagnetic background because of the non-abelian field nature, which was first recognized by Nielsen and Olesen (N-O) in a different context some time ago. We argue that characteristic features of the instabilities observed in the preceding simulations can be explained by identifying them as the N-O instability, and discuss possible implications to thermalization mechanism of the colliding system.