41 research outputs found
Coupled DM heating in SCDEW cosmologies
Strongly Coupled Dark Energy plus Warm dark matter (SCDEW) cosmologies admit
the stationary presence of of coupled-DM and DE, since
inflationary reheating. Coupled-DM fluctuations therefore grow up to
non-linearity even in the early radiative expansion. Such early non-linear
stages are modelized here through the evolution of a top-hat density
enhancement, reaching an early virial balance when the coupled-DM density
contrast is just 25-26 and DM density enhancement is of total
density. During the time needed to settle in virial equilibium, the virial
balance conditions however continue to modify, so that "virialized" lumps
undergo a complete evaporation. Here we outline that DM particles processed by
overdentities preserve a fraction of their virial momentum. Although fully
non-relativistic, the resulting velocities (moderately) affect the fluctuation
dynamics over greater scales, entering the horizon later on.Comment: 20 pages, 7 figures; updated to match the published versio
Dark Matter, Dark Energy and the solution of the strong CP problem
The strong CP problem was solved by Peccei & Quinn by introducing axions, a
viable candidate for Dark Matter (DM). Here the PQ approach is modified so to
yield also Dark Energy (DE). DM and DE arise, in fai proportions, from a single
scalar field, without tuning any extra parameter. In the present epoch, they
are weakly coupled. Fluctuations have a fair evolution. The model is also
fitted to the WMAP1 release, using a Markov Chain Monte Carlo technique, and
performs as well as CDM, coupled or uncoupled DE. Best--fit
cosmological parameters for different models are mostly within 2--
level. Here, the main peculiarity of the model is to favor high values of the
Hubble parameter.Comment: Proceeding of the workshop dsu2006, "The Dark Side of th Universe",
Madrid, June 20-24, 200