S-brane thermodynamics

Abstract

The description of string-theoretic s-branes at g(s)=0 as exact worldsheet CFTs with a lambda cosh X-0 or lambdae(+/-X 0) boundary interaction is considered. Due to the imaginary-time periodicity of the interaction under X-0-->X-0+2pii, these configurations have intriguing similarities to black hole or de Sitter geometries. For example, the open string pair production as seen by an Unruh detector is thermal at temperature T=1/4pi. It is shown that, despite the rapid time dependence of the s-brane, there exists an exactly thermal mixed state of open strings. The corresponding boundary state is constructed for both the bosonic and superstring cases. This state defines a long-distance euclidean effective field theory whose light modes are confined to the s-brane. At the critical value of the coupling lambda=1/2, the boundary interaction simply generates an SU(2) rotation by pi from Neumman to Dirichlet boundary conditions. The lambda=1/2 s-brane reduces to an array of sD-branes (D-branes with a transverse time dimension) on the imaginary time axis. The long range force between a (bosonic) sD-brane and an ordinary D-brane is shown from the annulus diagram to be 11/12 times the force between two D-branes. The linearized time-dependent RR field Fp+2=dC(p+l) produced by an sDp-brane in superstring theory is explicitly computed and found to carry a half unit of s-charge Q(s)=integral(Sigma 8-p) *Fp+2=1/2, where Sigma(8-p) is any transverse spacelike slice.