Constraints on the very early universe from thermal WIMP dark matter

Abstract

We investigate the relic density n χ of non-relativistic long-lived or stable particles χ in non-standard cosmological scenarios. We calculate the relic abundance starting from arbitrary initial temperatures of the radiationdominated epoch, and derive the lower bound on the initial temperature T 0 ≥ m χ /23, assuming that thermally produced χ particles account for the dark matter energy density in the universe; this bound holds for all χ annihilation cross sections. We also investigate cosmological scenarios with modified expansion rate. Even in this case an approximate formula similar to the standard one is capable of predicting the final relic abundance correctly. Choosing the χ annihilation cross section such that the observed cold dark matter abundance is reproduced in standard cosmology, we constrain possible modifications of the expansion rate at T ∼ m χ /20, well before Big Bang Nucleosynthesis.

Model-independent determination of the WIMP mass from direct dark matter detection data

“…Knowledge of the WIMP couplings will also permit prediction of the WIMP annihilation cross section. Together with the Dark Matter density inferred from cosmological observations, this will allow to test our understanding of the early universe [19]. A determination of the WIMP mass from Dark Matter detection experiments is thus a crucial ingredient in many analyses that shed light on the dark sector of the universe.…”

SUSY constraints, relic density, and very early universe

“…Entropy and energy alterations are considered here as effective effects, which can be generated by curvature, phase transitions, extra-dimensions, or other phenomena in the Early Universe. In a specific physical scenario, these parameters may be related, as for example in reheating models [19][20][21][22][23][24][25][26]. However, the large number of unanswered questions in the pre-BBN epoch and the complexity of particle physics models, which involves many different fields, can doubt the simplicity of reheating models.…”

“…However, before Big-Bang nucleosynthesis (BBN) many phenomena could have modified the physical properties of the Universe, such as the expansion rate, or the entropy evolution, or even the non-thermal production of relic particles. The calculation of the relic density is altered in these cases, and for example the influence of a quintessence-like scalar field [10][11][12][13][14][15][16][17][18], or reheating and non thermal production of relic particles due to the decay of an inflaton-like scalar field [19][20][21][22][23][24][25][26] have already been discussed in the literature. Scenarios involving dark fluids or extra-dimensions modifying the expansion rate of the Universe have been also considered in [27].…”

Collider physics and cosmology

“…3.2, one therefore simultaneously bounds contributions ∆ρ to H. This approach has been explored in a few recent studies [44,45,46]. In Ref.…”