Near-Thermal Radiation in Detectors, Mirrors and Black Holes: A Stochastic Approach

TL;DR

This paper presents a stochastic approach to understanding near-thermal radiation phenomena like the Unruh and Hawking effects, especially in non-ideal conditions with asymptotic horizons or finite-time accelerations.

Contribution

It introduces a unifying stochastic framework that models quantum vacuum fluctuations as arising from exponential scale transformations, extending analysis to non-ideal spacetime scenarios.

Findings

Radiance observed in systems with asymptotic horizons or finite acceleration.

Deviations from perfect Planckian spectra are quantified by a parameter measuring departure from ideal conditions.

Results have implications for non-equilibrium black hole thermodynamics and semiclassical gravity.

Abstract

In analyzing the nature of thermal radiance experienced by an accelerated observer (Unruh effect), an eternal black hole (Hawking effect) and in certain types of cosmological expansion, one of us proposed a unifying viewpoint that these can be understood as arising from the vacuum fluctuations of the quantum field being subjected to an exponential scale transformation. This viewpoint, together with our recently developed stochastic theory of particle-field interaction understood as quantum open systems described by the influence functional formalism, can be used to address situations where the spacetime possesses an event horizon only asymptotically, or none at all. Examples studied here include detectors moving at uniform acceleration only asymptotically or for a finite time, a moving mirror, and a collapsing mass. We show that in such systems radiance indeed is observed, albeit not in a precise Planckian spectrum. The deviation therefrom is determined by a parameter which measures the departure from uniform acceleration or from exact exponential expansion. These results are expected to be useful for the investigation of non-equilibrium black hole thermodynamics and the linear response regime of backreaction problems in semiclassical gravity.