Particle creation, renormalizability conditions and the mass-energy spectrum in gravity theories of quadratic Lagrangians

TL;DR

This paper investigates massive scalar particle production in a five-dimensional quadratic gravity theory, deriving renormalizability conditions, exact solutions, and analyzing the resulting mass-energy spectrum and late-time particle creation.

Contribution

It provides new insights into particle creation mechanisms, renormalizability conditions, and the mass-energy spectrum in quadratic gravity theories with extra dimensions.

Findings

Particles are mainly created near singular epochs.

Renormalizability conditions constrain particle production.

Analytic expressions for late-time particle number and energy density are derived.

Abstract

Massive scalar particle production, due to the anisotropic evolution of a five-dimensional spacetime, is considered in the context of a quadratic Lagrangian theory of gravity. Those particles, corresponding to field modes with non-vanishing momentum component along the fifth dimension, are created mostly in the neighbourhood of a singular epoch where only their high-frequency behaviour is of considerable importance. At the 1-loop approximation level, general renormalizability conditions on the physical quantities relevant to particle production are derived and discussed. Exact solutions of the resulting Klein-Gordon field equation are obtained and the mass-energy spectrum attributed to the scalar field due to the cosmological evolution is being investigated further. Finally, analytic expressions regarding the number and the energy density of the created particles at late times, are also derived and discussed.