Me. Ortiz et F. Vendrell, Thermal radiation in nonstatic curved spacetimes: Quantum mechanical path integrals and configuration space topology - art. no. 084005, PHYS REV D, 5908(8), 1999, pp. 4005
A quantum mechanical path integral derivation is given of a thermal propaga
tor in non-static Gui's spacetime. The thermal nature of the propagator is
understood in terms of homotopically non-trivial paths in the configuration
space appropriate to tortoise coordinates. The connection to thermal emiss
ion from collapsing black holes is discussed. [S0556-2821(99)01106-6].