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arXiv · 2505.00366

Primordial black hole formation from a type II perturbation in the absence and presence of pressure

Koichiro Uehara·Albert Escrivà·Tomohiro Harada·Daiki Saito·Chul-Moon Yoo
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Abstract

We investigate primordial black holes (PBHs) formed from extremely large amplitudes of primordial curvature fluctuations, classified as type II. Type II fluctuations differ from type I by the presence of a stationary point on the initial time slice, when we see the areal radius as a function of the radial coordinate. Starting from these type II perturbations to form black holes, the nonlinear evolution governed by the Einstein equations generally results in two distinct types, A and B, of horizon configurations, respectively characterized by the absence and presence of a bifurcating trapping horizon where past and future trapping horizons meet. In this paper, we use the Lemaitre-Tolman-Bondi solution to show that type I/II and type A/B classifications are equivalent for a spherically symmetric dust fluid system, regardless of the fluctuation profile. However, this equivalence does not generally hold in the presence of pressure.

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Koichiro Uehara, Albert Escrivà, Tomohiro Harada, Daiki Saito, Chul-Moon Yoo. 2025-05-01. Primordial black hole formation from a type II perturbation in the absence and presence of pressure. https://arxiv.org/abs/2505.00366

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