NANOGrav spectral index γ=3 from melting domain walls

Jul 10, 2023
7 pages
Published in:
  • Phys.Rev.D 108 (2023) 12, 123529
  • Published: Dec 15, 2023
e-Print:
DOI:

Citations per year

20222023202403429
Abstract: (APS)
We discuss cosmic domain walls described by a tension redshifting with the expansion of the Universe. These melting domain walls emit gravitational waves with the low-frequency spectral shape Ωgwf2 corresponding to the spectral index γ=3 favored by the recent NANOGrav 15 yrs data. We discuss a concrete high-energy physics scenario leading to such a melting domain wall network in the early Universe. This scenario involves a feebly coupled scalar field, which can serve as a promising dark matter candidate. We identify parameters of the model matching the gravitational wave characteristics observed in the NANOGrav data. The dark matter mass is pushed to the ultralight range below 10-1110-12eV which is accessible through planned observations thanks to the effects of superradiance of rotating black holes.
Note:
  • 7 revtex pages, 1 figure; added references and appendix with the calculation of gravitational wave spectrum; matches version accepted in PRD
  • domain wall: network
  • dark matter: mass
  • black hole: rotation
  • coupling: scalar
  • field theory: scalar
  • NANOGrav
  • power spectrum
  • spectral
  • tension
  • gravitational radiation
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