Accelerating cold dark matter cosmology (Ω _Λ ≡ 0)

Abstract

A new kind of accelerating flat model with no dark energy that is fully dominated by cold dark matter (CDM) is investigated. The number of CDM particles is not conserved and the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational particle creation. A related work involving accelerating CDM cosmology has been discussed before the SNe observations [Lima, Abramo & Germano, Phys. Rev. D53, 4287 (1996)]. However, in order to have a transition from a decelerating to an accelerating regime at low redshifts, the matter creation rate proposed here includes a constant term of the order of the Hubble parameter. In this case, H0 does not need to be small in order to solve the age problem and the transition happens even if the matter creation is negligible during the radiation and part of the matter dominated phase. Therefore, instead of the vacuum dominance at redshifts of the order of a few, the present accelerating stage in this sort of Einstein-de Sitter CDM cosmology is a consequence of the gravitational particle creation process. As an extra bonus, in the present scenario does not exist the coincidence problem that plagues models with dominance of dark energy. The model is able to harmonize a CDM picture with the present age of the universe, the latest measurements of the Hubble parameter and the Supernovae observations. PACS numbers: 95.35.+d,95.30.Tg

Observational constraints on interacting dark matter model without dark energy

“…This situation is mathematically equivalent to the gravitational DM particle creation process within the context of non-equilibrium thermodynamics (Lima et al 2008). The Hubble parameter is now given by…”

“…Basilakos & Plionis (2009) investigated the circumstances under which the analytical solution space within the framework of the interacting dark matter (IDM) scenario allows for a late accelerated phase of the Universe, and find that the effective annihilation term of the simplest IDM model is quite small by using the nine observational H(z) data points of Simon et al (2005). The gravitational matter creation model that is fully dominated by cold dark matter (Lima et al 2008;Basilakos & Lima 2010) is mathematically equivalent to one case of the IDM models (Basilakos & Plionis 2009).…”

Could dark matter interactions be an alternative to dark energy?

“…The corresponding effects on the global dynamics of the particle creation regime, which provides an effective negative pressure, has also been investigated by a number of authors (e.g., Prigogine et al 1989;Lima et al 2008, and references therein).…”

“…Other sources of negative pressure have been proposed, including gravitational matter "creation" processes (Zeldovich 1970), modeled by non-equilibrium thermodynamics (Prigogine et al 1989) or even the C-field of Hoyle & Narlikar (1966). The effects of the former proposal (gravitational matter creation) on the global dynamics of the universe have been investigated, based on the assumption that the particles created are non-interacting (Lima et al 2008). The merit of all these alternative models is that they unify the dark sector (dark energy and dark matter), since a single dark component (the dark matter) needs to be introduced into the cosmic fluid.…”

“…It is interesting to note that this case can be viewed as a generalization of the gravitational matter creation model of Prigogine et al (1989) (see also Lima et al 2008, and references therein) in which annihilation processes are also included, although the matter-creation component dominates over annihilations. In this scenario, as in any interacting dark-matter model with a left-over residual radiation, a possible contribution from the radiation products to the global dynamics is negligible, as we show in Appendix A.…”