Brane-antibrane systems at finite temperature and the entropy of black branes

We consider D-brane/anti-D-brane systems at T>0. Starting at the closedstring vacuum, we argue that a finite temperature leads to the reappearance ofopen string degrees of freedom. We also show that, at a sufficiently largetemperature, the open string vacuum becomes stable. Building upon thisobservation and previous work by Horowitz, Maldacena and Strominger, weformulate a microscopic brane-antibrane model for the non-extremal blackthree-brane in ten dimensions (as well as for the black two- and five-branes ineleven dimensions). Under reasonable assumptions, and using known results fromthe AdS/CFT correspondence, the microscopic entropy agrees with thesupergravity result up to a factor of 2^(p/p+1), with p the dimension of thebrane. The negative specific heat and pressure of the black brane have a simpleinterpretation in terms of brane-antibrane annihilation. We also find in themodel states resembling black holes and other lower-dimensional black branes.Comment: LaTeX 2e, 36 pages, 2 eps figures. v2: References adde