Constraints on the maximal number of dark degrees of freedom from black hole evaporation, cosmic rays, colliders, and supernovae

TL;DR

This paper reviews and updates constraints on the maximum number of dark sector particles from various astrophysical, cosmological, and collider observations, considering different mass regimes and effects.

Contribution

It provides a comprehensive analysis of constraints on dark degrees of freedom, incorporating recent data and detailed considerations of light and massless particles.

Findings

Black hole evaporation limits on dark particles

Constraints from supernova energy loss

Collider production bounds

Abstract

A dark sector with a very large number of massive degrees of freedom is generically constrained by radiative corrections to Newton's constant. However, there are caveats to this statement, especially if the degrees of freedom are light or mass-less. Here, we examine in detail and update a number of constraints on the possible number of dark degrees of freedom, including from black hole evaporation, from perturbations to systems including an evaporating black hole, from direct gravitational production at colliders, from high-energy cosmic rays, and from supernovae energy losses.