Damping of inhomogeneities in neutralino dark matter

TL;DR

This paper demonstrates that neutralino dark matter experiences a sharp cut-off in its primordial density fluctuation spectrum due to damping mechanisms, setting a lower limit on the mass of the smallest dark matter structures.

Contribution

It identifies and quantifies the damping effects in neutralino dark matter, establishing a minimal mass scale for the formation of dark matter structures.

Findings

Primordial spectrum has a sharp cut-off due to damping.

Minimal mass for neutralino dark matter structures is above 10^(-6) solar masses.

Damping mechanisms include collisional damping and free streaming.

Abstract

The lightest supersymmetric particle, most likely the neutralino, might account for a large fraction of dark matter in the Universe. We show that the primordial spectrum of density fluctuations in neutralino cold dark matter (CDM) has a sharp cut-off due to two damping mechanisms: collisional damping during the kinetic decoupling of the neutralinos at O(10 MeV) and free streaming after last scattering of neutralinos. The cut-off in the primordial spectrum defines a minimal mass for CDM objects in hierarchical structure formation. For typical neutralino and sfermion masses the first gravitationally bound neutralino clouds have masses above 10^(-6) M_\odot.