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Millisecond pulsars are making more than 100 rotations per second. Crucially, for some of them the period of rotation is constant with a relative precision similar to atomic-clock-based time standards when averaged over decades. Thus millisecond pulsars are amazing clocks. Recent results on 15 years of observation for the timing of 68 millisecond pulsars strongly suggest that there are gravitational waves with wavelengths in the light years range, thus waves roughly as long as a typical distance between stars in the galaxy. These results were published in June 2023 by the NANOGrav collaboration -– the North American Nanohertz Observatory for Gravitational Waves and other Pulsar Timing Arrays teams.
In our paper we demonstrated that this gravitational wave background can be from melting domain walls which were built out of dark matter in the early universe before the first nuclei were formed.
We demonstrated that, contrary to more conservative astrophysical options, like mergers of supermassive black holes, our early universe model can perfectly well explain the spectrum (distribution of energy in frequency bands) of gravitational waves observed by the NANOGrav collaboration.
Contact person: Alexander Vikman