PRIMORDIAL BLACK HOLE PAIR CREATION IN R2 THEORY

1998 ◽  
Vol 13 (28) ◽  
pp. 2289-2293 ◽  
Author(s):  
B. C. PAUL ◽  
S. MUKHERJEE ◽  
G. P. SINGH ◽  
A. BEESHAM
Keyword(s):  
Black Holes ◽  
Semiclassical Approximation ◽  
Pair Creation ◽  
Quadratic Term ◽  
Inflationary Universe ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
De Sitter ◽  
Gravitational Action ◽  
Spatial Section

The probability for quantum creation of an inflationary universe with a pair of black holes has been studied in semiclassical approximation with Hartle–Hawking boundary conditions, assuming a gravitational action which includes a quadratic term in the scalar curvature αR2, α being a constant. The action of the instanton responsible for creating such a universe, with a spatial section with S1×S2 topology, is seen to be less than that of a de Sitter S3 instanton, unless α<-1/(8Λ), where Λ is the cosmological constant. Since negative α implies a classical instability, the probability for production of primordial black holes seems to be suppressd in R2-theory.

scholarly journals PROBABILITY FOR PRIMORDIAL BLACK HOLES IN HIGHER DERIVATIVE THEORIES

2002 ◽  
Vol 11 (04) ◽  
pp. 493-501 ◽  
Author(s):  
B. C. PAUL ◽  
ARINDAM SAHA
Keyword(s):  
Boundary Condition ◽  
Black Holes ◽  
Cosmological Constant ◽  
Semiclassical Approximation ◽  
Inflationary Universe ◽  
Primordial Black Holes ◽  
Relative Probability ◽  
Gravitational Action ◽  
Higher Derivative ◽  
Spatial Section

The probability for quantum creation of an inflationary universe with a pair of black holes in higher derivative theories has been studied. Considering a gravitational action which includes quadratic (αR2) and/or cubic term (βR3) in scalar curvature in addition to a cosmological constant (Λ) in semiclassical approximation with Hartle–Hawking boundary condition, the probability has been evaluated. The action of the instanton responsible for creating such a universe, with spatial section with S1XS2 topology, is found to be less than that with a spatial S3 topology, unless α < - 1/8Λ in R2-theory. In the R3 theory, however, there exists a set of solutions without a cosmological constant when βR2 = 1 and [Formula: see text] which admit primordial black holes (PBH) pair in an inflationary universe scenario. We note further that when βR2 ≠ 1, one gets PBH pairs in the two cases: (i) with α and Λ both positive and (ii) with Λ positive and α negative satisfying a constraint 6|α|Λ < 1. However, the relative probability for creation of an inflationary universe with a pair of black holes in the R3-theory suppresses when [Formula: see text] or [Formula: see text]. However, if the above constraints are relaxed one derives interesting results leading to a universe with PBH in R3-theory without cosmological constant.

GRAVITATIONAL INSTANTONS: RECENT DEVELOPMENTS

2002 ◽  
Vol 17 (15n17) ◽  
pp. 1123-1133 ◽  
Author(s):  
S. MUKHERJEE ◽  
B. C. PAUL
Keyword(s):  
Black Holes ◽  
Quantum Cosmology ◽  
Quadratic Term ◽  
Inflationary Universe ◽  
Primordial Black Holes ◽  
Gravitational Instantons ◽  
Higher Derivative ◽  
Recent Developments ◽  
Universe Problem ◽  
Hilbert Action

Recent developments in the semiclassical quantum cosmology have been reviewed. Two processes have been considered in detail: (i) creation of an inflationary universe with a pair of Primordial Black Holes and (ii) the quantum creation of an open inflationary universe. While the first makes use of standard non-singular instanton, the second process has been described by a singular Hawking-Turok (HT) instanton. To examine the efficacy of the techniques and also to check the robustness of the results, the processes have been studied in higher derivative theories, including αR2 and βR3 terms to the Hilbert action. It has been shown that with α > 0, the quadratic term suppresses the production of primordial black holes. For the open universe problem in the higher derivative theory, the parameters needed for the occurrence of the HT instanton are found to be highly constrained. Moreover, the legitimacy of HT instantons remains to be established, although considerable activities in this field have been reported.

scholarly journals A constraint on light primordial black holes from the interstellar medium temperature

2021 ◽  
Author(s):  
Hyungjin Kim
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Dwarf Galaxy ◽  
Dark Matter Candidate ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Substantial Fraction ◽  
Interstellar Gas ◽  
Medium Temperature ◽  
Fast Electrons

Abstract Primordial black holes are a viable dark matter candidate. They decay via Hawking evaporation. Energetic particles from the Hawking radiation interact with interstellar gas, depositing their energy as heat and ionization. For a sufficiently high Hawking temperature, fast electrons produced by black holes deposit a substantial fraction of energy as heat through the Coulomb interaction. Using the dwarf galaxy Leo T, we place an upper bound on the fraction of primordial black hole dark matter. For M &lt; 5 × 10−17M⊙, our bound is competitive with or stronger than other bounds.

scholarly journals The Merger Rate of Black Holes in a Primordial Black Hole Cluster

Physics ◽  
2021 ◽  
Vol 3 (2) ◽  
pp. 372-378
Author(s):  
Viktor D. Stasenko ◽  
Alexander A. Kirillov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mass Spectrum ◽  
Star Clusters ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Central Black Hole ◽  
Solar Mass ◽  
Merger Rate

In this paper, the merger rate of black holes in a cluster of primordial black holes (PBHs) is investigated. The clusters have characteristics close to those of typical globular star clusters. A cluster that has a wide mass spectrum ranging from 10−2 to 10M⊙ (Solar mass) and contains a massive central black hole of the mass M•=103M⊙ is considered. It is shown that in the process of the evolution of cluster, the merger rate changed significantly, and by now, the PBH clusters have passed the stage of active merging of the black holes inside them.

On Primordial Black Holes and secondary gravitational waves generated from inflation with solo/multi-bumpy potential

2021 ◽  
Author(s):  
Rui feng Zheng ◽  
Jia ming Shi ◽  
Taotao Qiu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Waves ◽  
Power Spectra ◽  
Small Scale ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Slow Roll ◽  
Spherical Collapse ◽  
Scalar Perturbations

Abstract It is well known that primordial black hole (PBH) can be generated in inflation process of the early universe, especially when the inflaton field has some non-trivial features that could break the slow-roll condition. In this paper, we investigate a toy model of inflation with bumpy potential, which has one or several bumps. We found that potential with multi-bump can give rise to power spectra with multi peaks in small-scale region, which can in turn predict the generation of primordial black holes in various mass ranges. We also consider the two possibilities of PBH formation by spherical collapse and elliptical collapse. And discusses the scalar-induced gravitational waves (SIGWs) generated by the second-order scalar perturbations.

scholarly journals PRIMORDIAL BLACK HOLE FORMATION FROM INFLATON

2000 ◽  
Vol 09 (06) ◽  
pp. 705-710 ◽  
Author(s):  
XIN HE MENG ◽  
BIN WANG ◽  
S. FENG
Keyword(s):  
Black Hole ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
De Sitter ◽  
Hole Formation ◽  
Black Hole Formation ◽  
Expansion Of The Universe ◽  
Slow Rolling ◽  
The Relationship ◽  
The Universe

Measurements of the distances to SNe Ia have produced strong evidence that the expansion of the Universe is really accelarating, implying the existence of a nearly uniform component of dark energy with the simplest explanation as a cosmological constant. In this paper a small changing cosmological term is proposed, which is a function of a slow-rolling scalar field, by which the de Sitter primordial black holes' properties, for both charged and uncharged cases, are carefully examined and the relationship between the black hole formation and the energy transfer of the inflaton is eluciated. The criterion for primordial black hole formation is given.

scholarly journals EVOLUTION OF PRIMORDIAL BLACK HOLE MASS SPECTRUM IN BRANS–DICKE THEORY

2013 ◽  
Vol 22 (05) ◽  
pp. 1350022 ◽  
Author(s):  
D. DWIVEDEE ◽  
B. NAYAK ◽  
L. P. SINGH
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mass Spectrum ◽  
Energy Density ◽  
Analytic Solutions ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Black Hole Mass ◽  
Linear And Nonlinear ◽  
The Universe

We investigate the evolution of primordial black hole mass spectrum by including both accretion of radiation and Hawking evaporation within Brans–Dicke (BD) cosmology in radiation-, matter- and vacuum-dominated eras. We also consider the effect of evaporation of primordial black holes on the expansion dynamics of the universe. The analytic solutions describing the energy density of the black holes in equilibrium with radiation are presented. We demonstrate that these solutions act as attractors for the system ensuring stability for both linear and nonlinear situations. We show, however, that inclusion of accretion of radiation delays the onset of this equilibrium in all radiation-, matter- and vacuum-dominated eras.

scholarly journals Large power spectrum and primordial black holes in the effective theory of inflation

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Guillermo Ballesteros ◽  
Sebastián Céspedes ◽  
Luca Santoni
Keyword(s):  
Power Spectrum ◽  
Energy Scale ◽  
Effective Theory ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
De Sitter ◽  
Effective Coupling ◽  
Large Power ◽  
Single Field ◽  
Large Quantum

Abstract We study the generation of a large power spectrum, necessary for primordial black hole formation, within the effective theory of single-field inflation. The mechanisms we consider include a transition into a ghost-inflation-like phase and scenarios where an exponentially growing mode is temporarily turned on. In the cases we discuss, the enhancement in the power spectrum results from either a swift change in some effective coupling or a modification of the dispersion relation for the perturbations, while the background evolution remains unchanged and approximately de Sitter throughout inflation. The robustness of the results is guaranteed thanks to a weakly broken galileon symmetry, which protects the effective couplings against large quantum corrections. We discuss how the enhancement of the power spectrum is related to the energy scale of the operators with weakly broken galileon invariance, and study the limits imposed by strong coupling and the validity of the perturbative expansion.

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