Resonant high energy graviton to photon conversion at post recombination epoch

TL;DR

This paper investigates how high energy gravitons can resonantly convert into photons in cosmic magnetic fields after recombination, potentially creating an observable gamma-ray background and linking primordial black holes to cosmic radiation backgrounds.

Contribution

It demonstrates that resonant conversion significantly enhances photon production from gravitons, suggesting observable signatures and connecting primordial black holes to cosmic radiation backgrounds.

Findings

Resonant conversion probability exceeds non-resonant cases.

Produced photons could dominate the cosmic X-ray background.

Lower mass primordial black holes shift the spectrum to ultraviolet and optical ranges.

Abstract

Resonant conversion of high energy gravitons into photons in large scale cosmological magnetic fields at the post recombination epoch is considered. It is shown that the probability of the resonance photon production is much higher than the non-resonant one. As a result an observable isotropic background of cosmic gamma rays might be created. As shown in our previous paper, an early population of primordial black holes (PBHs) prior to big bang nucleosynthesis (BBN) could be an efficient source of high frequency gravitational waves. For the primordial black hole mass about $10^8$ g the produced photons would be the dominant component of the soft to hard Cosmic X-ray Background (CXB) and for lower masses the spectrum is shifted down to the ultraviolet and optic.