Could dark matter interactions be an alternative to dark energy?

¹ Research Center for Astronomy, Academy of Athens, 11527 Athens, Greece e-mail: svasil@academyofathens.gr; mplionis@astro.noa.gr
² Institute of Astronomy & Astrophysics, National Observatory of Athens, Thessio 11810, Athens, Greece & Instituto Nacional de Astrofísica, Óptica y Electrónica, 72000 Puebla, Mexico

Received: 6 June 2009
Accepted: 3 August 2009

Abstract

We study the global dynamics of the universe within the framework of the interacting dark matter (IDM) scenario. Assuming that the dark matter obeys the collisional Boltzmann equation, we can derive analytical solutions of the global density evolution, that can accommodate an accelerated expansion, equivalent to either the quintessence or the standard Λ models, with the present time located after the inflection point. This is possible if there is a disequilibrium between the DM particle creation and annihilation processes with the former process dominating, which creates an effective source term with negative pressure. Comparing the predicted Hubble expansion of one of the IDM models (the simplest) with observational data, we find that the effective annihilation term is quite small, as suggested by various experiments.