Thermal radiation in curved spacetime using influence functional formalism

Abstract: Generalizing to relativistic exponential scaling and using the theory of noise from quantum fluctuations, it has been shown that one vacuum (Rindler, Hartle-Hawking, or Gibbons-Hawking for the cases of the uniformly accelerated detector, black hole, and de-Sitter universe, respectively) can be understood as resulting from the scaling of quantum noise in another vacuum. We explore this idea more generally to establish a flat spacetime and curved spacetime analogy. For this purpose, we start by examining noise kernels for free fields in some well-known curved spacetimes, e.g., the spacetime of a charged black hole, the spacetime of a Kerr black hole, Schwarzschild-de Sitter, Schwarzschild anti-de Sitter, and Reissner-Nordstrom de-Sitter spacetimes. Here, we consider a maximal analytical extension for all these spacetimes and different vacuum states. We show that the exponential scale transformation is responsible for the thermal nature of radiation.