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T: Fachverband Teilchenphysik

T 24: Theoretische Astroteilchenphysik und Kosmologie II

T 24.1: Vortrag

Donnerstag, 18. März 2010, 16:45–17:00, HG XV

Preheating Dark Matter — •Ole Bjaelde — RWTH Aachen

From simulations of structure formation with cold dark matter (CDM) it is becoming clear that the CDM paradigm cannot be the ultimate truth. More specifically simulations with CDM over-predict the amount of small galaxies orbiting a typically-sized galaxy like the Milky Way and predict too cuspy density profiles in the inner region of CDM halos.

Here we present a novel approach to alleviate these problems in which a coherently oscillating scalar field, interpreted as dark matter, can decay into standard model particles. Specifically, we consider a scalar field with sub-eV mass decaying into a Fermi sea of neutrinos. Like the case of fermionic preheating, we find that Pauli blocking controls the dark matter decay into the neutrino sea. The radius of the Fermi sphere depends on the expansion of the universe leading to a time-varying equation of state of dark matter. This makes the scenario very rich and we show that the decay rate might be different at different cosmological epochs. We categorize this in two interesting regimes and then study the cosmological perturbations to find the impact on structure formation.