CMB and Large Scale Structure as a test of Mixed Models with n>1

Abstract

We compute CBR anisotropies in mixed models with different hot components, including neutrinos or volatile HDM arising from the decay of heavier particles. The CBR power spectra of these models exhibit a higher doppler peak than CDM, and the discrepancy is even stronger in volatile models when the decay gives rise also to a neutral scalar. CBR experiments, together with Large Scale Structure (LSS) data, are then used to constrain the space parameter of mixed models, when values of the primeval spectral index n > 1 are also considered. Even if n>1 is allowed, however, LSS alone prescribes that \Omega_h \mincir 0.30. LSS can be fitted by taking simultaneously a low derelativization redshift z_der (down to \simeq 600) and a high n, while CBR data from baloon--borne experiment cause a severe selection on this part of the parameter space. In fact, while late derelativization and $n>1$ have opposite effects on the fluctuation spectrum P(k), they sum their action on the angular spectrum C_l. Henceforth n \magcir 1.3 seems excluded by baloon--borne experiment outputs, while a good fit of almost all CBR and LSS data is found for Omega_h values between 0.11 and 0.16, n \sim 1.1 and z_der \sim 2000--5000. A smaller n is allowed, but z_der should never be smaller than \simeq 1200.