Boundary String Field Theory Approach to High-Temperature Tachyon Potential

The boundary string field theory approach is used to evaluate the one-loop tachyon potential. We first discuss the boundary condition at the two boundaries on annulus diagram and then the exact form of corrected potentials at zero and high temperature are obtained. The profile of the tachyon potential is found to be temperature independent and tachyon will condense at high temperature. Our investigations also provide an easy way to prove the universality of the tachyon potential, even if the string is in the thermal background.