Primordial Magnetic Fields and Stochastic GW Backgrounds

TL;DR

This paper explores how primordial magnetic fields influence stochastic gravitational wave backgrounds and how they can relax existing bounds from big bang nucleosynthesis, with implications for future gravitational wave detection.

Contribution

It presents new insights into the role of primordial magnetic fields as sources of gravitational radiation and their impact on the spectral properties of stochastic GW backgrounds.

Findings

Primordial magnetic fields can significantly alter the thermal history of the Universe.

Magnetic fields may relax the bounds on stochastic GW backgrounds from BBN.

Spectral properties of stochastic GW backgrounds are affected by relic magnetic fields.

Abstract

Operating resonant mass detectors set interesting bounds on diffused backgrounds of gravitational radiation and in the next five years the wide-band interferometers will also look for stochastic sources. In this lecture the interplay among relic GW backgrounds and large scale magnetic fields will be discussed. Magnetic fields may significantly affect the thermal history of the Universe in particular at the epoch electroweak symmetry breaking and shortly after. A review of some old an new results on the spectral properties of stochastic GW backgrounds will be presented. The possible r\^ole of primordial magnetic fields as a source of gravitational radiation will be outlined. It will be shown that the usual bound on stochastic GW backgrounds coming from the standard big bang nucleosynthesis (BBN) scenario can be significantly relaxed.