Collapse threshold for a cosmological Klein-Gordon field

Hidalgo, Juan Carlos; Santiago, Josué De; Germán, Gabriel; Barbosa-Cendejas, Nandinii; Ruiz-Luna, Waldemar

doi:10.1103/physrevd.96.063504

Cited by 34 publications

(37 citation statements)

References 56 publications

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“…For example, a PBH formed in an early dust-like era of mass M ≈ 10 −16 M , would collapse in ∼ 10 −20 seconds. This is perfectly consistent with PBH formation timescales and our result may complement previous work assessing the formation of PBHs in an early dust-like era [39,[41][42][43]. Our result also argues in favour of recent work on the formation of PBHs from non-spherical configurations [14,22].…”

Section: Discussion and Final Remarkssupporting

confidence: 92%

Black hole formation from the gravitational collapse of a nonspherical network of structures

et al. 2018

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We examine the gravitational collapse and black hole formation of multiple non-spherical configurations constructed from Szekeres dust models with positive spatial curvature that smoothly match to a Schwarzschild exterior. These configurations are made of an almost spherical central core region surrounded by a network of "pancake-like" overdensities and voids with spatial positions prescribed through standard initial conditions. We show that a full collapse into a focusing singularity, without shell crossings appearing before the formation of an apparent horizon, is not possible unless the full configuration becomes exactly or almost spherical. Seeking for black hole formation, we demand that shell crossings are covered by the apparent horizon. This requires very special fine-tuned initial conditions that impose very strong and unrealistic constraints on the total black hole mass and full collapse time. As a consequence, non-spherical non-rotating dust sources cannot furnish even minimally realistic toy models of black hole formation at astrophysical scales: demanding realistic collapse time scales yields huge unrealistic black hole masses, while simulations of typical astrophysical black hole masses collapse in unrealistically small times. We note, however, that the resulting time-mass constraint is compatible with early Universe models of primordial black hole formation, suitable in early dust-like environments. Finally, we argue that the shell crossings appearing when non-spherical dust structures collapse are an indicator that such structures do not form galactic mass black holes but virialise into stable stationary objects.

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Section: Discussion and Final Remarkssupporting

confidence: 92%

Black hole formation from the gravitational collapse of a nonspherical network of structures

et al. 2018

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“…In section 4.2 we point out that string moduli typically satisfy requirement I) for the formation of compact structures even in the cases of potentials (or initial conditions) that do not support tachyonic oscillations, parametric JHEP08(2018)070 resonance, spinning axion solutions or phase transitions. Similar results have already been obtained in the past in [111][112][113][114]. The fulfillment of condition II) requires detailed and model-dependent numerical studies of the non-linear evolution of the overdensities including the effects of gravity.…”

Section: Jhep08(2018)070supporting

confidence: 83%

Moduli stars

Krippendorf¹,

Muia

Quevedo

2018

J. High Energ. Phys.

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We explore the possibility that (Bose-Einstein) condensation of scalar fields from string compactifications can lead to long-lived compact objects. Depending on the type of scalar fields we find different realisations of star-like and solitonic objects. We illustrate in the framework of type IIB string compactifications that closed string moduli can lead to heavy microscopic stars with masses of order V α M Planck , α = 1, 3/2, 5/3 where V is the volume of the extra dimensions. Macroscopic compact objects from ultra-light string axions are realised with masses of order e V 2/3 M Planck . Q-ball configurations can be obtained from open string moduli whereas the closed string sector gives rise to a new class of solutions, named PQ-balls, that arise in the two-field axion-modulus system. The stability, the potential for the formation, and the observability of moduli stars through gravitational waves are discussed. In particular we point out that during the early matter phase given by moduli domination, density perturbations grow by a factor V β with β > 2 and non-linear effects cannot be neglected.

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“…More dramatically, it has been proposed that the Universe may become effectively pressureless for some early period. For example, this may occur due to its energy density being channelled into non-relativistic massive particles [16,25,26] or due to slow reheating after inflation [15,[27][28][29][30]. In the latter case, the field which is responsible for reheating the Universe typically oscillates about the minimum of its potential V (φ), with w having an average value of zero.…”

Section: Introductionmentioning

confidence: 99%

Primordial black hole formation during slow reheating after inflation

et al. 2018

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We study the formation of primordial black holes (PBHs) in the early Universe during a period of slow reheating after inflation. We demonstrate how the PBH formation mechanism may change even before the end of the matter-dominated phase and calculate the expected PBH mass function. We find that there is a threshold for the variance of the density contrast, σc 0.05, below which the transition occurs even before reheating, with this having important consequences for the PBH mass function. We also show that there is a maximum cut-off for the PBH mass at around 100 M , below which the subdominant radiation bath affects PBH production, making the scenario particularly interesting for the recent LIGO observations of black hole mergers.

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Collapse threshold for a cosmological Klein-Gordon field

Cited by 34 publications

References 56 publications

Black hole formation from the gravitational collapse of a nonspherical network of structures

Black hole formation from the gravitational collapse of a nonspherical network of structures

Moduli stars

Primordial black hole formation during slow reheating after inflation

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