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تسجيل مستخدم جديدNANOGrav signal as mergers of Stupendously Large Primordial Black Holes
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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 $Msim(10^{11}-10^{12})M_{odot}$, 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 $Mlesssim 10^{11}M_{odot}$ could both fit NANOGrav and respect $mu$ distortions limits, they become excluded from large scale structure constraints.
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We consider the observational constraints on stupendously large black holes (SLABs) in the mass range $M gtrsim 10^{11},M_{odot}$. These have attracted little attention hitherto and we are aware of no published constraints on a SLAB population in the
range $(10^{12}$ - $10^{18}),M_{odot}$. However, there is already evidence for black holes of up to nearly $10^{11},M_{odot}$ in galactic nuclei, so it is conceivable that SLABs exist and they may even have been seeded by primordial black holes. We focus on limits associated with (i) dynamical and lensing effects, (ii) the generation of background radiation through the accretion of gas during the pregalactic epoch, and (iii) the gamma-ray emission from the annihilation of the halo of weakly interacting massive particles (WIMPs) expected to form around each SLAB if these provide the dark matter. Finally, we comment on the constraints on the mass of ultra-light bosons from future measurements of the mass and spin of SLABs.
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