The fast life of holographic mesons

Abstract

We use holographic techniques to study meson quasiparticles moving through a thermal plasma in N=2 super-Yang-Mills theory, with gauge group SU(Nc) and coupled to Nf flavours of fundamental matter. This holographic approach reliably describes the system at large Nc, large 't Hooft coupling and Nf/Nc<<1. The meson states are destabilized by introducing a small quark density nq. 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 qcrit. While the spectral functions do not display isolated resonances for q>qcrit, 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>>qcrit.