NANOGrav signal as mergers of Stupendously Large Primordial Black Holes

We give an explanation for the signal detected by NANOGrav as the stochastic gravitational wave background from binary mergers of primordial Stupendously Large Black Holes(SLABs) of mass M similar to (10(11) - 10(12)) M-circle dot, and corresponding to roughly 0.1% of the dark matter. We show that the stringent bounds coming from mu distortions of the CMB can be surpassed if the perturbations resulting in these BHs arise from the non-Gaussian distribution of fluctuations expected in single field models of inflation generating a spike in the power spectrum. While the tail of the stochastic background coming from binaries with M less than or similar to 10(11)M(circle dot) could both fit NANOGrav and respect mu distortions limits, they become excluded from large scale structure constraints.

Automated summary

The study suggests that the signal detected by NANOGrav could be from the stochastic gravitational wave background of binary mergers of primordial Stupendously Large Black Holes, which contribute roughly 0.1% of the dark matter. Overcoming the stringent limits from mu distortions of the CMB is possible if the perturbations in these black holes derive from the expected non-Gaussian distribution of fluctuations. However, the stochastic background from binaries with masses less than or equal to 10^11M-solar masses is excluded by constraints from large scale structure.