Finite-temperature amplitudes in open-string systems

I present an analysis of tree and one-loop finite-temperature amplitudes in open-string systems. Temperature is introduced through a recently developed real-time formalism for string thermodynamics and formal expressions for various cases are obtained. I point out the origin of divergences in the temperature-dependent amplitudes and show the emergence of the maximum (Hagedorn) temperature at the one-loop level for the open bosonic string and the open (type-I) superstring in the Ramond-Neveu-Schwarz formulation. I also discuss the problem of the tachyon stabilization by temperature effects as well as renormalization, symmetry, and supersymmetry breaking at finite temperature