The fast life of holographic mesons

We use holographic techniques to study meson quasiparticles moving through a thermal plasma in N = 2 super-Yang-Mills theory, with gauge group SU(N-c) and coupled to N-f flavours of fundamental matter. This holographic approach reliably describes the system at large N-c, large 't Hooft coupling and N-f/N-c << 1. The meson states are destabilized by introducing a small quark density n(q). Spectral functions are used to examine the dispersion relations of these quasiparticles. In a low-momentum regime, the quasiparticles approach a limiting velocity which can be significantly less than the speed of light. In this regime, the widths of the quasiparticles also rise dramatically as their momentum approaches a critical value q(crit). While the spectral functions do not display isolated resonances for q > q(crit), the dispersion relations can be extended into this high-momentum regime by studying the dual quasinormal modes. A preliminary qualitative analysis of these modes suggests that the group velocity rises to the speed of light for q >> q(crit).