How hot are expanding universes ?

Abstract

A way to address the conundrum of Quantum Gravity is to illustrate the potentially fundamental interplay between quantum field theory, curved space-times physics and thermodynamics. So far, when studying moving quantum systems in the vacuum, the only known perfectly thermal temperatures are those obtained for constant (or null) accelerations $A$ in constant (or null) Hubble parameters $H$ space-times. In this Letter, restricting ourselves to conformally coupled scalar fields, we present the most comprehensive expression for the temperature undergone by a moving observer in the vacuum, valid for any time-dependent linear accelerations and Hubble parameters: $T=\sqrt{A^2+H^2+2\dot{H}\dot{t}}/2\pi$ where $\dot t=\d t/\d\t$ is the motion's Lorentz factor. The inequivalence between a constant $T$ and actual thermality is explained. As a byproduct, all the Friedman universes for which observers at rest feel the vacuum as a thermal bath are listed.

4 pages, no figure, version accepted in PRD

References in corpus (12)

• A Phantom Menace? Cosmological consequences of a dark energy component with super-negative equation of state
• The Unruh effect and its applications
• Superquintessence
• Horizon Entropy
• Accelerated Detectors and Temperature in (Anti) de Sitter Spaces
• Acceleration Radiation for Orbiting Electrons
• Local Temperature in Curved Spacetime
• Comment on "Accelerated Detectors and Temperature in (Anti) de Sitter Spaces"
• Unruh response functions for scalar fields in de Sitter space
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• Uniformly Accelerated Mirrors. Part 2: Quantum Correlations
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Cited by in corpus (6)

• Experimental Observation of Acceleration-Induced Thermality
• Electroweak Vacuum Instability and Renormalized Higgs Field Vacuum Fluctuations in the Inflationary Universe
• Unruh--DeWitt detectors in spherically symmetric dynamical space-times
• Quantum detectors in generic non flat FLRW space-times
• Vacuum fluctuation of conformally coupled scalar field in FLRW space-times
• Wigner function method for the Gibbons-Hawking and the Unruh effect