On thermal radiation of de Sitter space in the semiclassical Jackiw-Teitelboim model

In general, the Gibbons-Hawking temperature based on the Euclidean functional approach shows that de Sitter space in the Bunch-Davies vacuum is globally thermal. In the exactly soluble semiclassical Jackiw-Teitelboim model, we investigate thermal property of de Sitter space by taking into account the quantum back reaction of the geometry. The temperature of de Sitter space in the Bunch-Davies vacuum is found to vanish. In case of a certain quantum state breaking the de Sitter symmetry, de Sitter space can be made thermally exited; however, in this case the dilaton singularity cannot be avoided. Consequently, in the Jackiw-Teitelboim model the temperature of de Sitter space in the Bunch-Davies vacuum turns out to be zero and the Bunch-Davies vacuum is found to be the only physical vacuum without any naked singularities.Comment: 14 pages, 1 figure, comments and references adde