Primordial black holes forming during kination: the trapped, the overdense, and the void
Abstract
We study primordial black-hole (PBH) formation in a single-field model which passes from slow roll, through a transient ultra-slow-roll phase, into kination. Nonlinear numerical-relativity simulations are used to follow localised, initially sub-Hubble field fluctuations across the non-attractor transition, to determine the resulting super-Hubble curvature profiles, and subsequently to evolve their re-entry during kination. Within the set of initial configurations explored here, we find three qualitatively distinct outcomes, namely a patch which remains trapped in inflation, a positive-curvature overdensity, and a negative-curvature void bounded by an overdense shell. Each may form a PBH, although by a different physical mechanism. For one selected profile in each of the overdense and void channels, we measure collapse thresholds and compare them with thresholds for sinc profiles. The comparison shows that neither the central curvature nor the peak linear compaction alone provides a profile- or channel-independent collapse criterion. PBH abundances in non-attractor models must therefore be formulated in terms of the distribution of complete profiles, with the trapped, overdense, and void channels treated separately.
Related
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- Inflaton accretion onto primordial black holes during reheating
- Long-term 3+1 simulations of primordial black hole formation during radiation domination
- From Kination to Detection: Scotogenic Scalar Dark Matter
- Third-order scalar induced gravitational waves during a matter-dominated era: secular growth and implications for primordial black hole domination
BibTeX
@misc{joana2026primordial,
title = {{Primordial black holes forming during kination: the trapped, the overdense, and the void}},
author = {Cristian Joana},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2607.20423},
eprint = {2607.20423},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.20423},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Primordial black holes forming during kination: the trapped, the overdense, and the void
AU - Cristian Joana
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2607.20423
UR - https://arxiv.org/abs/2607.20423
AB - We study primordial black-hole (PBH) formation in a single-field model which passes from slow roll, through a transient ultra-slow-roll phase, into kination. Nonlinear numerical-relativity simulations are used to follow localised, initially sub-Hubble field fluctuations across the non-attractor transition, to determine the resulting super-Hubble curvature profiles, and subsequently to evolve their re-entry during kination. Within the set of initial configurations explored here, we find three qualitatively distinct outcomes, namely a patch which remains trapped in inflation, a positive-curvature overdensity, and a negative-curvature void bounded by an overdense shell. Each may form a PBH, although by a different physical mechanism. For one selected profile in each of the overdense and void channels, we measure collapse thresholds and compare them with thresholds for sinc profiles. The comparison shows that neither the central curvature nor the peak linear compaction alone provides a profile- or channel-independent collapse criterion. PBH abundances in non-attractor models must therefore be formulated in terms of the distribution of complete profiles, with the trapped, overdense, and void channels treated separately.
ER -