Decaying massive particles in the matter and radiation dominated eras

Abstract

According to the standard model of cosmology, the early universe has been dominated by radiation or non-relativistic matter in several eras of its history. However, many cosmological calculations involving particle processes are commonly done using Minkowskian results for them, although, for more precise treatment, quantum field theory in curved spacetime is needed. This paper aims to fill this gap by presenting decay rates for matter and radiation dominated universes in this more precise treatment. We provide a study of the average decay rates for a process where a conformally coupled massive scalar field decays into massless scalar particles. It is found that the presence of a curved spacetime modifies the Minkowskian result considerably for early times but asymptotically only by an additive term proportional to the inverse of mass and interaction time. Thus, the correction is small for large time scales, but on the time scales of the order of m ∼ t, the relative correction term may be of importance.

Reheating via gravitational particle production in the kination epoch

“…It was found that Minkowskian and curved space decay rates produce results within the same order of magnitude with only small numerical differences. Although it is known that decay rates in curved space are modified from their Minkowskian counterparts [20,21,24], it is likely that the timescales in question are so small that the effect of curved space modification has not produced noticeable effects yet.…”

“…When curvature cannot be neglected anymore, Minkowskian decay rates are nevertheless only an approximation and curved space counterparts should be used instead. This problem has attained a wealth of interest in recent times and decay rates have been obtained for various processes [20][21][22]. For more on the conceptual and technical issues regarding particle decay in curved spacetime, we refer the reader articles [20-22, 25-27, 32, 33].…”

Scalar model of effective field theory in curved space

“…At the same time, the simplified versions of the model (1) are known as useful tools in cosmology. E.g., in the well-known papers [33,34] (see further references therein, also the recent work [35]) the scalar field χ describes the Bose-Einstein condensate of some more fundamental fields. The considerations in these works involves not only tree-level, but also the loop effects.…”

Particle decay in expanding Friedmann-Robertson-Walker universes

“…The only difference compared to the case of a real index is the different exponential factor with the consequence that it is not cancelled by the square of the absolute value in Eq. (14). Performing a change of variables to u = 2bmη (2+n)/2 /(2 + n), we are left with…”

“…In the present paper we focus on a more thorough treatment of particle decay in spatially flat Friedmann-Robertson-Walker (FRW) universes with a general power-law expansion and a priori unrestricted gravitational coupling, extending previous analyses of Refs. [14,15]. This was done using the method of added-up probabilities originally introduced in Ref.…”