Tracking through equality

We give a tracker solution for the quintessence scalar field for Ratra--Peebles or SUGRA potentials, holding before, during and after the equality epoch (\rho_m=\rho_r) and nicely fitting the numerical behavior.Comment: submitted to New Astronom

Recovery of fluctuation spectrum evolution from tomographic shear spectra

Forthcoming large angle surveys are planned to obtain high precision tomographic shear data. In principle, they will allow us to recover the spectra of matter density fluctuation, at various redshift, through the inversion of the expressions yielding shear from fluctuation spectra. This was discussed in previous work, where SVD techniques for matrix inversion were also shown to be the optimal tool to this aim. Here we show the significant improvements obtainable by using a 7 bin tomography, as allowed by future Euclid data, as well as the question of error propagation from shear to fluctuation spectra. We find that the technique is a promising tool, namely for the analysis of baryon physics throug high-l shear spectra and to test the consistency between expansion rate and fluctuation growth.Comment: 22 pages, 10 figure

Coupled DM heating in SCDEW cosmologies

Strongly Coupled Dark Energy plus Warm dark matter (SCDEW) cosmologies admit the stationary presence of $\sim 1\, \%$ 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 $\sim 10\, \%$ 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 $\Lambda$CDM, coupled or uncoupled DE. Best--fit cosmological parameters for different models are mostly within 2--$\sigma$ 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