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.

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 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 On stochastic effects and primordial black-hole formation

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Florian Kühnel ◽  
Katherine Freese
Keyword(s):  
Field Theory ◽  
Black Hole ◽  
Inflection Point ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Hole Formation ◽  
Stochastic Effects ◽  
Black Hole Formation ◽  
Large Quantum ◽  
Inflationary Models

AbstractThe effect of large quantum fluctuations on primordial black-hole formation for inflationary models with a quasi-inflection point is investigated. By using techniques of stochastic inflation in combination with replica field theory and the Feynman–Jensen variational method, it is non-perturbatively demonstrated that the abundance of primordial black holes is amplified by several orders of magnitude as compared to the classical computation.

scholarly journals Multi-Field versus Single-Field in the Supergravity Models of Inflation and Primordial Black Holes

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 115
Author(s):  
Sergei V. Ketov
Keyword(s):  
Power Spectra ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Second Stage ◽  
Slow Roll ◽  
Field Versus ◽  
Cosmological Observations ◽  
Minimal Supergravity ◽  
Single Field ◽  
Under Construction

We review the models unifying inflation and Primordial Black Hole (PBH) formation, which are based on the modified (Starobinsky-type) supergravity. We begin with the basic (Starobinsky) inflationary model of modified gravity and its alpha-attractor-type generalizations for PBH production, and recall how all those single-field models can be embedded into the minimal supergravity. Then, we focus on the effective two-field models arising from the modified (Starobinsky-type) supergravity and compare them to the single-field models under review. Those two-field models describe double inflation whose first stage is driven by Starobinsky’s scalaron and whose second stage is driven by another scalar belonging to the supergravity multiplet. The power spectra are numerically computed, and it is found that the ultra-slow-roll regime gives rise to the enhancement (peak) in the scalar power spectrum leading to an efficient PBH formation. The resulting PBH masses and their density fraction (as part of dark matter) are found to be in agreement with cosmological observations. The PBH-induced gravitational waves, if any, are shown to be detectable by the ground-based and space-based gravitational interferometers under construction.

scholarly journals PRIMORDIAL BLACK HOLE CONSTRAINTS FOR CURVATON MODELS WITH PREDICTED LARGE NON-GAUSSIANITY

2013 ◽  
Vol 22 (07) ◽  
pp. 1350034 ◽  
Author(s):  
E. V. BUGAEV ◽  
P. A. KLIMAI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Power Spectrum ◽  
Mass Spectra ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Curvature Perturbation ◽  
Small Scales ◽  
Non Gaussian ◽  
Spectrum Amplitude

We consider the early Universe scenario which allows for production of non-Gaussian curvature perturbations at small scales. We study the peculiarities of a formation of primordial black holes (PBHs) connected with the non-Gaussianity. In particular, we show that PBH constraints on the values of curvature perturbation power spectrum amplitude are strongly dependent on the shape of perturbations and can significantly (by two orders of magnitude) deviate from the usual Gaussian limit [Formula: see text]. We give examples of PBH mass spectra calculations and PBH constraints for the particular case of the curvaton model.

scholarly journals Small-scale primordial fluctuations in the 21cm Dark Ages signal

2020 ◽  
Author(s):  
Philippa S Cole ◽  
Joseph Silk
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Power Spectrum ◽  
High Redshift ◽  
Power Spectra ◽  
Mass Range ◽  
Small Scale ◽  
Primordial Black Hole ◽  
Small Scales ◽  
Single Field

Abstract Primordial black hole production in the mass range 10 − 104 M⊙ is motivated respectively by interpretations of the LIGO/Virgo observations of binary black hole mergers and by their ability to seed intermediate black holes which would account for the presence of supermassive black holes at very high redshift. Their existence would imply a boost in the primordial power spectrum if they were produced by overdensities reentering the horizon and collapsing after single-field inflation. This, together with their associated Poisson fluctuations would cause a boost in the matter power spectrum on small scales. The extra power could become potentially observable in the 21cm power spectrum on scales around k ∼ 0.1 − 50 Mpc−1 with the new generation of filled low frequency interferometers. We explicitly include the contribution from primordial fluctuations in our prediction of the 21cm signal which has been previously neglected, by constructing primordial power spectra motivated by single-field models of inflation that would produce extra power on small scales. We find that depending on the mass and abundance of primordial black holes, it is important to include this contribution from the primordial fluctuations, so as not to underestimate the 21cm signal. Evidently our predictions of detectability, which lack any modelling of foregrounds, are unrealistic, but we hope that they will motivate improved cleaning algorithms that can enable us to access this intriguing corner of PBH-motivated parameter space.

scholarly journals Constant-rate inflation: primordial black holes from conformal weight transitions

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Kin-Wang Ng ◽  
Yi-Peng Wu
Keyword(s):  
Black Holes ◽  
Power Spectrum ◽  
Analytic Solutions ◽  
Conformal Weight ◽  
Late Time ◽  
Primordial Black Holes ◽  
De Sitter ◽  
Slow Roll ◽  
Time Scaling ◽  
Constant Rate

Abstract Constant-rate inflation, including ultra-slow-roll inflation as a special case, has been widely applied to the formation of primordial black holes with a significant deviation from the standard slow-roll conditions at both the growing and decaying phases of the power spectrum. We derive analytic solutions for the curvature perturbations with respect to the late-time scaling dimensions (conformal weights) constrained by the dilatation symmetry of the de Sitter background and show that the continuity of conformal weights across different rolling phases is protected by the adiabatic condition of the inflaton perturbation. The temporal excitation of subleading states (with the next-to-lowest conformal weights), recorded as the “steepest growth” of the power spectrum, is triggered by the entropy production in the transition from the slow-roll to the constant-rate phases.

scholarly journals Perturbative unitarity in quasi-single field inflation

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Suro Kim ◽  
Toshifumi Noumi ◽  
Keito Takeuchi ◽  
Siyi Zhou
Keyword(s):  
Quantum Gravity ◽  
Parameter Space ◽  
High Energy ◽  
New Physics ◽  
Energy Scale ◽  
Effective Theory ◽  
Massive Scalar ◽  
High Energy Scale ◽  
Single Field ◽  
High Energy Scattering

Abstract We study implications of perturbative unitarity for quasi-single field inflation with the inflaton and one massive scalar. Analyzing high energy scattering, we show that non-Gaussianities with |fNL| ≳ 1 cannot be realized without turning on interactions which violate unitarity at a high energy scale. Then, we provide a relation between fNL and the scale of new physics that is required for UV completion. In particular we find that for the Hubble scale H ≳ × 109 GeV, Planck suppressed operators can easily generate too large non-Gaussanities and so it is hard to realize successful quasi-single field inflation without introducing a mechanism to suppress quantum gravity corrections. Also we generalize the analysis to the regime where the isocurvature mode is heavy and the inflationary dynamics is captured by the inflaton effective theory. Requiring perturbative unitarity of the two-scalar UV models with the inflaton and one heavy scalar, we clarify the parameter space of the P(X, ϕ) model which is UV completable by a single heavy scalar.

scholarly journals Abundance of Primordial Black Holes in Peak Theory for an Arbitrary Power Spectrum

2020 ◽  
Author(s):  
Chul-Moon Yoo ◽  
Tomohiro Harada ◽  
Shin’ichi Hirano ◽  
Kazunori Kohri
Keyword(s):  
Mass Spectrum ◽  
Power Spectrum ◽  
Environmental Effect ◽  
Window Function ◽  
Radial Coordinate ◽  
Primordial Black Holes ◽  
Scale Invariant ◽  
Curvature Perturbation ◽  
Arbitrary Power ◽  
Nonlinear Relation

Abstract We modify the procedure to estimate PBH abundance proposed in Ref. [1] so that it can be applied to a broad power spectrum such as the scale-invariant flat power spectrum. In the new procedure, we focus on peaks of the Laplacian of the curvature perturbation △ ζ and use the values of △ ζ and △ △ ζ at each peak to specify the profile of ζ as a function of the radial coordinate while the values of ζ and △ ζ are used in Ref. [1]. The new procedure decouples the larger-scale environmental effect from the estimate of PBH abundance. Because the redundant variance due to the environmental effect is eliminated, we obtain a narrower shape of the mass spectrum compared to the previous procedure in Ref. [1]. Furthermore, the new procedure allows us to estimate PBH abundance for the scale-invariant flat power spectrum by introducing a window function. Although the final result depends on the choice of the window function, we show that the k-space tophat window minimizes the extra reduction of the mass spectrum due to the window function. That is, the k-space tophat window has the minimum required property in the theoretical PBH estimation. Our procedure makes it possible to calculate the PBH mass spectrum for an arbitrary power spectrum by using a plausible PBH formation criterion with the nonlinear relation taken into account.

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.

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