Contributions to the Study of Thermal States of the Bosonic String in the TFD Formalism

We determine the local entropy of the free energy of the quantized open bosonic string in Minkowski spacetime with the most general boundary conditions. We formulate a finite temperature theory of the thermal closed string excitations in anti-de Sitter spacetime within the TFD approach. We write down the thermal states and obtain the entropy and the free energy in the first order expansion of the semiclassical quantization in the center of mass reference frame.