  The holographic dual of a finite-temperature gauge theory with a small number
of flavours typically contains D-brane probes in a black hole background. At
low temperature the branes sit outside the black hole and the meson spectrum is
discrete and possesses a mass gap. As the temperature increases the branes
approach a critical solution. Eventually they fall into the horizon and a phase
transition occurs. In the new phase the meson spectrum is continuous and
gapless. At large N and large 't Hooft coupling, this phase transition is
always of first order, and in confining theories with heavy quarks it occurs at
a temperature higher than the deconfinement temperature for the glue.
