1. Negative pressure as a quantum effect in free-streaming in the cosmological background
- Author
-
Becattini, F. and Roselli, D.
- Subjects
General Relativity and Quantum Cosmology ,Astrophysics - Cosmology and Nongalactic Astrophysics ,High Energy Physics - Theory - Abstract
We present a study of energy density and pressure of a free real scalar quantum field after its decoupling from a thermal bath in the spatially flat Friedman-Lema\^itre-Robertson-Walker space-time by solving the Klein-Gordon equation both analytically and numerically for different predetermined scale factor functions $a(t)$. The energy density and pressure, defined by subtracting the vacuum expectation values at the decoupling time, feature corrections with respect to the classical free-streaming solution of the relativistic Boltzmann equation. We show that if the expansion rate is comparable or larger than $mc^2/\hbar$ or $KT_0/\hbar$ where $m$ is the mass and $T_0$ the decoupling temperature, both energy density and pressure get strong quantum corrections which substantially modify their classical dependence on the scale factor $a(t)$ and drive pressure to large negative values. For a minimally coupled field with a very low mass in an expanding de Sitter universe quantum corrections become dominant driving pressure and energy density to become asymptotically constant with an equation of state $p/\varepsilon \simeq -1$. For a minimally coupled massless field, quantum corrections are asymptotically dominant for any accelerated expansion., Comment: 28 pages, 15 figures. Added reference, other minor changes more...
- Published
- 2024