http://arxiv.org/abs/1807.00561
Primordial magnetic fields (PMFs) can source gravitational wave background (GWB). We In this paper, we investigate the possible constraints on small-scale PMF considering the ongoing and forthcoming direct detection observation of GWB. In contrast to the conventional cosmological probes, e.g., cosmic microwave background anisotropies, which is useful to investigate large-scale PMF ($>1~{\rm Mpc}$), 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 about $10^{2}~{\rm nG}$ on much smaller scales about $k\approx 10^{12}~{\rm Mpc}^{-1}$. We also demonstrate that the pulsar timing array has a potential to strongly constrain PMFs. The current limits on GWB from the pulsar timing array can put the tight constraint on the amplitude of the PMFs about $30~{\rm nG}$ whose coherent length is about $k\approx 10^{6}~{\rm Mpc}^{-1}$. The future experiments for the direct detection of GWB by the Square Kilometre Array could give much tighter constraints on the amplitude of PMFs about $5~{\rm nG}$ on $k\approx 10^{6}~{\rm Mpc}^{-1}$, on which scales, it is difficult to reach by using the cosmological observations.
S. Saga, H. Tashiro and S. Yokoyama
Tue, 3 Jul 18
68/95
Comments: 8 pages, 3 figures
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