1303.7038 (Jorge Mastache et al.)

Extra relativistic degrees of freedom without extra particles using
Planck data    [PDF]

Jorge Mastache, Axel de la Macorra

A recent number of analysis of cosmological data have shown indications for the presence of extra radiation beyond the standard model at equality and nucleosynthesis epoch, which has been usually interpreted as an effective number of neutrinos, Neff > 3.046. In this work we establish the theoretical basis for a particle physics-motivated model (Bound Dark Matter, BDM) which explain the need of extra radiation. The BDM model describes dark matter particles which are relativistic at a scale below aac due to non-perturbative methods, as protons and neutrons do, this process is described by a time dependent equation of state, w_bdm(a). We compute the range of values of the BDM model, xc=ac*vc, that explain the values obtain for the 4He at BBN and Neff at equality. Combining different analysis we conclude that this may happen in xc = 5.01 (^{+6.01}_{-5.01}) x 10^{-5} with a vc = 0.56 \pm 0.39. We conclude that we can account for the apparent extra radiation Nex using phase transition in the dark matter with a time dependent equation of state with no need for introducing extra relativistic particles.

View original: http://arxiv.org/abs/1303.7038