Eur. Phys. J. Plus (2012) 127: 18
https://doi.org/10.1140/epjp/i2012-12018-x

Regular Article

Standard Cosmology extended to include particle creation originated from Universe expansion

Standard Cosmology with particle creation

¹ GNFM, Dipartimento di Fisica dell’Università degli Studi di Milano, Via Celoria, 16, 20133, Milano, Italy
² Gruppo Nazionale per la Fisica Matematica, Sesto Fiorentino, Italy

^* e-mail: antonio.zecca@mi.infn.it

Received: 5 December 2011
Revised: 10 January 2012
Accepted: 26 January 2012
Published online: 16 February 2012

Abstract

The Standard Cosmological model is extended to include particles created by Universe expansion. Accordingly, the density ρ and pressure p are modified by the adjoint of terms in the form , . Such expressions are based on results, previously obtained, relative to field quantization in curved space-time for spin 0 , 1/2 , 1 . The model is discussed in general and for special physical configurations. The case p = wρ is solved in the flat space-time case, and is discussed in some special asymptotic cases, leaving, however, the problem of determining α(t), β(t) open. The matter- and radiation-dominated models, analogous to those of the Standard Cosmology, are studied by choosing α(t), β(t) to be constant in time. The two models are integrated in the flat space-time case and both allow a numerical evaluation of the parameter Ω _0c relative to particle creation. Such value lies into the expected range. The results support the expectation that particle production plays an active role in the formulation of the cosmological model. Its importance should, however, be tested also in open and closed models and within a discussion including all kinds of energy contributions in the cosmological Einstein equation.