S-Brane Thermodynamics

TL;DR

This paper analyzes the thermodynamic properties of s-branes in string theory, revealing their thermal states, boundary conditions, and interactions with D-branes, with implications for understanding time-dependent backgrounds and black hole analogies.

Contribution

It provides an exact worldsheet CFT description of s-branes, constructs their boundary states, and computes their interactions and RR fields, highlighting novel thermal and boundary phenomena.

Findings

Open string pair production is thermal at temperature 1/4 pi.

At lambda=1/2, s-branes become arrays of sD-branes with half-unit s-charge.

The force between sD-branes and D-branes is 11/12 of the D-D force.

Abstract

The description of string-theoretic s-branes at g_s=0 as exact worldsheet CFTs with a (lambda cosh X^0) or (lambda e^(X^0)) boundary interaction is considered. Due to the imaginary-time periodicity of the interaction under X^0 -> X^0 + 2 pi i, 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 = 1/4 pi. 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 F=dC produced by an sD-brane in superstring theory is explicitly computed and found to carry a half unit of s-charge Q_s=\int_S *F=1/2, where S is any transverse spacelike slice.