The initial spin probability distribution of primordial black holes

By V. D. Luca, V. Desjacques, G. Franciolini, A. Malhotra, A. Riotto. Journal of Cosmology and Astroparticle Physics, 2019

156 citations recorded by the source corpus.

We study the spin of primordial black holes produced by the collapse of large inhomogeneities in the early universe. Since such primordial black holes originate from peaks, that is, from maxima of the local overdensity, we resort to peak theory to obtain the probability distribution of the spin at formation. We show that the spin is a first-order effect in perturbation theory: it results from the action of first-order tidal gravitational fields generating first-order torques upon horizon-crossing, and from the asphericity of the collapsing object. Assuming an ellipsoidal shape, the typical value of the dimensionless parameter as=S/GN M2, where S is the spin and M is the mass of the primordial black hole, is about (Ωdm/π) σδ√1−γ2. Here, σ2δ is the variance of the overdensity at horizon crossing, Ωdm measures the current abundance of the dark matter and the parameter γ is a measure of the width of the power spectrum giving rise to primordial black holes. One has γ=1 for monochromatic spectra. For these narrow spectra, the suppression arises because the velocity shear, which is strongly correlated with the inertia tensor, tends to align with the principal axis frame of the collapsing object. Typical values of as are at the percent level.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/e2e4a912f7ad88a503f2a738d50edcabe39ab6c1

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In Astronomy and Astrophysics

1. A. Riotto
2. G. Franciolini
3. V. D. Luca
4. M. Raidal
5. P. Pani
6. B. Carr
7. V. Vaskonen
8. H. Veermae

In Nuclear and High Energy Physics

1. A. Riotto
2. G. Franciolini
3. M. Raidal
4. H. Veermae
5. V. D. Luca
6. Gert Hütsi
7. P. Pani
8. V. Vaskonen

Citations in the corpus

• The evolution of primordial black holes and their final observable spins (2020, background): “The estimated PBH spin at formation is [35]”
• Two populations of LIGO-Virgo black holes (2020, background): “The initial spins of PBHs are expected to be tiny [32– 34] since they form at the highest density peaks in the primordial plasma that tend to have a spherical symmetry [35].”