Effects of the electromagnetic interaction upon particle creation in Robertson-Walker universes. II. A soluble example

Abstract

For pt.I see ibid., vol.2, no.3, p.373-80 (1985). The author evaluates the contributions n33(D) and n33(M) to the creation of electron-positron pairs and photons which are due to the electromagnetic interaction and compare them with the creation of 'free' electron-positron pairs (nF(D)=(bm)32//(2 pi 3C3)). As the cosmological model the author considers a time-symmetrically contracting and expanding radiation-domination Friedman universe with the conformal scale factor C2( eta )=b2 eta 2, (b=constant). The dependence of n33(D) and n33(M) on the details of the expansion (the slowness parameter b) and the particle mass m is the same as that of nF(D). Thus in all cosmological models considered here the relation n33(D)/n33(M) is equal to a constant which is less than 2, independently of both b and m. Ultra-relativistic electron-positron pair are created neither as free particles nor in consequence of the interaction. In the non-relativistic case the electromagnetic interaction yields a small but not insignificant contribution to particle creation near the Compton time of the Dirac particles. For non-relativistic (NR) electrons and positrons with almost equal amounts of their momenta we get n33(D,NR)=0.82n33(M)=1.49*10-4nF(D).