Primordial black hole formation for an anisotropic perfect fluid: initial conditions and estimation of the threshold

Musco, Ilia; Papanikolaou, Theodoros

doi:10.48550/arxiv.2110.05982

Cited by 4 publications

(4 citation statements)

References 70 publications

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“…In this paper, we focus on the PBH formation in a nonspherical setting and possible generation of the black hole spin. Although spherically symmetric dynamics for PBH formation has been mainly considered [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] for many years, we can also find several works in which nonspherical PBH formation is considered [50][51][52][53][54][55][56][57][58][59]. Some of them [50,51,53] focus on the PBH formation in a matter-dominated universe, in which the non-spherical collapse would be essential for understanding the criterion of the PBH formation.…”

Section: Introductionmentioning

confidence: 99%

Threshold of primordial black hole formation in nonspherical collapse

2020

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We perform the numerical simulation of primordial black hole formation from a nonspherical profile of the initial curvature perturbation ζ. We consider the background expanding universe filled with the perfect fluid with the linear equation of state p = wρ (w = 1/3 or 1/5), where p and ρ are the pressure and the energy density, respectively. The initial condition is set in a way such that the principal directions of the second derivatives of ζ and △ζ at the central peak are misaligned, where △ is the Laplacian. In this setting, since the linearized density is proportional to △ζ, the inertia tensor and deformation tensor ∂ i ∂ j ζ are misaligned. Thus tidal torque may act and the spin of a resultant primordial black hole would be non-zero in general, although it is estimated to be very small from previous perturbative analyses. As a result, we do not find a finite value of the spin within our numerical precision, giving support for the negligibly small value of the black hole spin for 1/5 ≲ w ≲ 1/3. More specifically, our results suggest that the dimensionless PBH spin s is typically so small that s ≪ 0.1 for w ≳ 0.2.

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Section: Introductionmentioning

confidence: 99%

Threshold of primordial black hole formation in nonspherical collapse

2020

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“…With regards to the PBH formation threshold value, δ c , the latter will depend, in general, on the shape of the collapsing curvature perturbation profile [89,90], on the EoS parameter at the time of PBH formation [91][92][93], as well on the presence of anisotropies [94] and nonsphericities [95,96]. In our case, we consider the standard case of spherical isotropic collapse in the HBB RD expanding era.…”

Section: Jcap06(2024)066mentioning

confidence: 99%

Primordial black holes and induced gravitational waves in non-singular matter bouncing cosmology

Papanikolaou,

Banerjee,

Cai

et al. 2024

J. Cosmol. Astropart. Phys.

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We present a novel model-independent generic mechanism for primordial black hole formation within the context of non-singular matter bouncing cosmology. In particular, considering a short transition from the matter contracting phase to the Hot Big Bang expanding Universe, we find naturally enhanced curvature perturbations on very small scales which can collapse and form primordial black holes. Interestingly, the primordial black hole masses that we find can lie within the observationally unconstrained asteroid-mass window, potentially explaining the totality of dark matter. Remarkably, the enhanced curvature perturbations, collapsing to primordial black holes, can induce as well a stochastic gravitational-wave background, being potentially detectable by future experiments, in particular by SKA, PTAs, LISA and ET, hence serving as a new portal to probe the bouncing nature of the initial conditions prevailing in the early Universe.

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“…As modes are stretched on super-horizon scales during inflation, curvature perturbations freeze-out until they re-enter the horizon during the post-inflationary epoch. At this point, if the amplitude of perturbations is larger than the threshold [44][45][46][47][48][49][50][51], they can collapse forming a population of PBHs with masses controlled by the energy contained in a Hubble volume. Various observations already constrain the fraction of DM composed of PBHs (usually denoted f PBH ≡ Ω PBH /Ω DM ).…”

Section: Introductionmentioning

confidence: 99%

Hunt for Light Primordial Black Hole Dark Matter with Ultra-High-Frequency Gravitational Waves

Franciolini¹,

Maharana²,

Muia³

2022

Preprint

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Light primordial black holes may comprise a dominant fraction of the dark matter in our Universe. This paper critically assesses whether planned and future gravitational wave detectors in the ultra-high-frequency band could constrain the fraction of dark matter composed of sub-solar primordial black holes. Adopting the state-of-the-art description of primordial black hole merger rates, we compare various signals with currently operating and planned detectors. As already noted in the literature, our findings confirm that detecting individual primordial black hole mergers with currently existing and operating proposals remains difficult. Current proposals involving gravitational wave to electromagnetic wave conversion in a static magnetic field and microwave cavities feature a technology gap with respect to the loudest gravitational wave signals from primordial black holes of various orders of magnitude. However, we point out that one recent proposal involving resonant LC circuits represents the best option in terms of individual merger detection prospects in the range (1 ÷ 100) MHz. In the same frequency range, we note that alternative setups involving resonant cavities, whose concept is currently under development, might represent a promising technology to detect individual merger events. We also show that a detection of the stochastic gravitational wave background produced by unresolved binaries is possible only if the theoretical sensitivity of the proposed Gaussian beam detector is achieved. Such a detector, whose feasibility is subject to various caveats, may be able to rule-out some scenarios for asteroidal mass primordial black hole dark matter. We conclude that pursuing dedicated studies and developments of gravitational wave detectors in the ultra-high-frequency band remains motivated and may lead to novel probes on the existence of light primordial black holes.

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Primordial black hole formation for an anisotropic perfect fluid: initial conditions and estimation of the threshold

Cited by 4 publications

References 70 publications

Threshold of primordial black hole formation in nonspherical collapse

Threshold of primordial black hole formation in nonspherical collapse

Primordial black holes and induced gravitational waves in non-singular matter bouncing cosmology

Hunt for Light Primordial Black Hole Dark Matter with Ultra-High-Frequency Gravitational Waves

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