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ABSTRACT We obtain constraints on cosmological parameters from the spherically averaged redshift-space correlation function of the CMASS Data Release 9 (DR9) sample of the Baryonic Oscillation Spectroscopic Survey (BOSS). We combine this information with additional data from recent cosmic microwave background (CMB), supernova and baryon acoustic oscillation measurements. Our results show no significant evidence of deviations from the standard flat Λ cold dark matter model, whose basic parameters can be specified by Ωm = 0.285 ± 0.009, 100 Ωb = 4.59 ± 0.09, ns = 0.961 ± 0.009, H0 = 69.4 ± 0.8 km s−1 Mpc−1 and σ8 = 0.80 ± 0.02. The CMB+CMASS combination sets tight constraints on the curvature of the Universe, with Ω k = −0.0043 ± 0.0049, and the tensor-to-scalar amplitude ratio, for which we find r < 0.16 at the 95 per cent confidence level (CL). These data show a clear signature of a deviation from scale invariance also in the presence of tensor modes, with ns < 1 at the 99.7 per cent CL. We derive constraints on the fraction of massive neutrinos of fν < 0.049 (95 per cent CL), implying a limit of ∑ mν < 0.51 eV. We find no signature of a deviation from a cosmological constant from the combination of all data sets, with a constraint of wDE = −1.033 ± 0.073 when this parameter is assumed time-independent, and no evidence of a departure from this value when it is allowed to evolve as wDE( a) = w0 + w a(1 − a). The achieved accuracy on our cosmological constraints is a clear demonstration of the constraining power of current cosmological observations. [ABSTRACT FROM AUTHOR]

We provide a short overview into Self Interacting Warm Dark Matter (SI-WDM) models from the context of Cosmological Perturbation Theory (CPT). The aim is to generalize conventional Cold DM models, by proposing a more general framework both from theoretical as well as from numerical fronts, on the effects of SI-WDM on the linear power spectrum and its consequent imprints on non-linear structure formation. After describing the theoretical background, we present useful analytic expressions for the collision terms in the Boltzmann Hierarchies, and provide some numerical results within the Relaxation Time Approximation (RTA). We consider massive DM particles that decouple from the hot plasma while relativistic. We introduce elastic DM–DM interactions under an ansatz for the scattering amplitude that accounts for massive mediators on an effective way. Paying special attention to the self interaction decoupling mechanisms, we analyze scenarios where the particle undergoes self decoupling while relativistic as well as while non relativistic. [ABSTRACT FROM AUTHOR]