Dark Radiation Emerging After Big Bang Nucleosynthesis?

TL;DR

Recent cosmic microwave background data hints at extra radiation produced after big bang nucleosynthesis, possibly from decay of non-relativistic matter, with constraints and scenarios explored.

Contribution

The paper introduces a general framework for how late-time radiation can emerge from matter decay, with specific models and observational constraints.

Findings

Extra radiation density may originate after BBN.

Decay of non-relativistic matter can produce this radiation.

Constraints on properties of decaying matter are established.

Abstract

We show how recent data from observations of the cosmic microwave background may suggest the presence of additional radiation density which appeared after big bang nucleosynthesis. We propose a general scheme by which this radiation could be produced from the decay of non-relativistic matter, we place constraints on the properties of such matter, and we give specific examples of scenarios in which this general scheme may be realized.