Universal behaviors of speed of sound from holography

Abstract

We investigate the speed of sound in (d + 1)-dimensional quantum field theory by studying its dual (d thorn 2)-dimensional gravity theory from gauge/gravity correspondence. Instead of the well-known conformal limit c(s)(2) -> 1/d at high temperature, we reveal two more universal quantities in various limits: c(s)(2) -> (d - 1)/16 pi at low temperature and c(s)(2) -> (d - 1)/16 pi d at large chemical potential.