Physics (Internal)

Partially Cannibalistic Dark Matter

This event is part of the Departmental Seminars.

Abstract: In the standard model of cosmology the dark matter is composed entirely of cold particles without any interactions other than gravitational, and it guides the formation of the matter structure of the Universe. This model has been successful in explaining the data coming from cosmological observations.

Nevertheless, as these observations become more accurate, discrepancies in the values for the matter power spectrum have surfaced, between those values directly measured by weak lensing experiments, and those obtained with global fits to the cosmic microwave background. This suggests that the dark matter might have a subdominant component (of order few % of the total dark matter) that does not form structure and therefore suppresses the spectrum.

In this talk I study the possibility that this component is a "cannibalistic" dark matter: composed of particles that "cannibalize" themselves to keep warm through large 3-to-2 interactions. This keeps the cannibal overdensities from falling in gravitational wells, thereby suppressing matter structure. I will present the mechanism through which this suppression occurs by solving the equations for the evolution of the energy density perturbations; suggest a particle physics toy model that realizes the cannibal behavior, and propose some possible UV completions.