"Early Cannibal Domination and the Matter Power Spectrum"

Decoupled hidden sectors in the early universe can easily and generically result in departures from radiation domination prior to BBN, leaving a potentially observable footprint in the distribution of dark matter on very small scales.   I'll talk about the gravitational consequences of an era of early cannibal domination, which can happen when the lightest particle in a hidden sector has efficient number-changing interactions, giving it an equation of state intermediate between radiation and matter. An early cannibal-dominated era generates a peak in the dark matter power spectrum, with the scale and amplitude of the peak directly determined by the mass of the cannibal field, the strength of the cannibal interactions, and its lifetime.  I'll discuss the map between the particle properties of the cannibal species and the features in the (linear) matter power spectrum, with an eye toward observability.