Hidden sectors and a multi-temperature universe

TL;DR

This paper explores the concept of a multi-temperature universe with hidden sectors, analyzing how different heat baths influence dark matter properties, dark forces, and the potential role of dark photons as dark matter candidates.

Contribution

It introduces a formalism for analyzing multi-temperature sectors in cosmology and applies it to explain velocity-dependent dark matter interactions and the viability of dark photons as dark matter.

Findings

Dark photon exchange can produce velocity-dependent cross sections.

Hidden sectors can have different heat baths from the visible sector.

Dark photons may constitute a significant portion of dark matter.

Abstract

A variety of supergravity and string based models contain hidden sectors which can play a role in particle physics phenomena and in cosmology. In this note we discuss the possibility that the visible sector and the hidden sectors in general live in different heat baths. Further, it is entirely possible that dark matter resides partially or wholly in hidden sectors in the form of dark Dirac fermions, dark neutralinos or dark photons. A proper analysis of dark matter and of dark forces in this case requires that one deals with a multi-temperature universe. We discuss the basic formalism which includes the multi-temperature nature of visible and hidden sectors in the analysis of phenomena observable in the visible sectors. Specifically we discuss the application of the formalism for explaining the velocity dependence of dark matter cross sections as one extrapolates from galaxy scales to scales of galaxy clusters. Here the dark photon exchange among dark fermions can produce the desired velocity dependent cross sections consistent with existing galactic cross section data indicating the existence of a new fifth (dark) force. We also discuss the possibility that the dark photon may constitute a significant portion of dark matter. We demonstrate a realization of this possibility in a universe with two hidden sectors and with the visible sector and the hidden sectors in different heat baths which allows a satisfaction of the constraints that the dark photon have a lifetime larger than the age of the universe and that its relic density be consistent with Planck data. Future directions for further work are discussed.