Limits on primordial magnetic fields from direct detection experiments of gravitational wave background

Understand

Primordial magnetic fields (PMFs) can source gravitational wave background (GWB).

• In this paper, we investigate the possible constraints on small-scale PMF considering the ongoing and forthcoming direct detection observations of GWB.
• In contrast to the conventional cosmological probes, e.g., cosmic microwave background anisotropies, which are useful to investigate large-scale PMFs ($>1 {\rm Mpc}$), the direct detection experiments of GWB can explore small-scale PMFs whose scales correspond to the observed frequencies of GWB.
• We show that future ground-based or space-based interferometric gravitational wave detectors give a strong constraint of about $10^{2} {\rm nG}$ on much smaller scales of about $k\approx 10^{12} {\rm Mpc}^{-1}$.