2017年10月
Spins of primordial black holes formed in the matter-dominated phase of the Universe
PHYSICAL REVIEW D
- ,
- ,
- ,
- 巻
- 96
- 号
- 8
- 開始ページ
- 083517
- 終了ページ
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1103/PhysRevD.96.083517
- 出版者・発行元
- AMER PHYSICAL SOC
Angular momentum plays very important roles in the formation of primordial black holes in the matter-dominated phase of the Universe if it lasts sufficiently long. In fact, most collapsing masses are bounced back due to centrifugal force, since angular momentum significantly grows before collapse. For masses with q <= q(c) similar or equal to 2.4I(1/3)sigma(1/3)(H), where q is a nondimensional initial quadrupole moment parameter, sigma(H) is the density fluctuation at horizon entry t = t(H), and I is a parameter of the order of unity, angular momentum gives a suppression factor similar to exp (-0.15I(4/3)sigma(-2/3)(H)) to the production rate. As for masses with q > q(c), the suppression factor is even stronger as similar to exp(-0.0046q(4)/sigma(2)(H)). We derive the spin distribution of primordial black holes and find that most of the primordial black holes are rapidly rotating near the extreme value a(*) = 1, where a(*) is the nondimensional Kerr parameter at their formation. The smaller sigma(H) is, the stronger the tendency towards the extreme rotation. Combining this result with the effect of anisotropy, we numerically and semianalytically estimate the production rate beta(0) of primordial black holes. Then we find that beta(0) similar or equal to 1.9 x 10(-6) f(q)(q(c))I-6 sigma(2)(H) exp(-0.15I(4/3)sigma(-2/3)(H) for sigma(H) less than or similar to 0.005, while beta(0). 0.05556 sigma(5)(H) for 0.005 less than or similar to sigma(H) less than or similar to 0.2, where f(q)(q(c)) is the fraction of masses whose q is smaller than q(c) and we assume f(q)(q(c)) is not too small. We argue that matter domination significantly enhances the production of primordial black holes despite the suppression factor. If the end time t(end) of the matter-dominated phase satisfies t(end) less than or similar to (0.4I sigma(H))(-1)t(H), the effect of the finite duration significantly suppresses primordial black hole formation and weakens the tendency towards large spins.
- リンク情報
- ID情報
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- DOI : 10.1103/PhysRevD.96.083517
- ISSN : 2470-0010
- eISSN : 2470-0029
- Web of Science ID : WOS:000413168800001