Abundance Of Primordial Black Holes Research Articles

Impact of primordial black holes on heavy neutral leptons searches in the framework of resonant leptogenesis

We investigate the effects on sub-TeV resonant leptogenesis of primordial black holes with masses from 106 g to ∼109 g. The latter might dominate the energy content of the Universe altering its evolution and, eventually, diluting the final baryon asymmetry. We find that, depending on the mass and abundance of primordial black holes, the parameter space of sub-TeV resonant leptogenesis shrinks towards higher right-handed neutrino masses and smaller active-sterile mixing. Remarkably, this translates into important implications for the experimental searches of heavy neutral leptons. Conversely, we demonstrate that a possible future detection of sub-TeV heavy neutral leptons would disfavor regions of the parameter space of primordial black holes currently allowed. Published by the American Physical Society 2024

Correction to: Abundance of primordial black holes in peak theory for an arbitrary power spectrum

Correction to: Abundance of primordial black holes in peak theory for an arbitrary power spectrum

Correction to Primordial black hole abundance from random Gaussian curvature perturbations and a local density threshold

Correction to Primordial black hole abundance from random Gaussian curvature perturbations and a local density threshold

Critical points in Palatini Higgs inflation with small non-minimal coupling

We investigate inflation driven by the Higgs boson in the Palatini formulation of General Relativity. Our analysis primarily focuses on a small non-minimal coupling of the Higgs field to gravity in the range 0 < ξ ≲ 1. We incorporate the renormalization group running of the relevant parameters as computed within the Standard Model and allow for small corrections. In addition to ξ, our model features two tunable parameters: the low-energy value of the top Yukawa coupling and an effective jump of the Higgs self-interaction. Our results indicate that critical points leading to a large enhancement of the power spectrum can be produced. However, the observed amplitude of perturbations in the CMB cannot be matched within this setting. On the one hand, this makes it difficult to generate a sizable abundance of primordial black holes. On the other hand, our findings can be viewed as very positive since they provide further evidence that Palatini Higgs inflation has favourable high-energy properties due to robustness against quantum corrections.

Spectators no more! How even unimportant fields can ruin your Primordial Black Hole model

In this work we terminate inflation during a phase of Constant Roll by means of a waterfall field coupled to the inflaton and a spectator field. The presence of a spectator field means that inflation does not end at a single point, ϕ e, but instead has some uncertainty resulting in a stochastic end of inflation. We find that even modestly coupled spectator fields can drastically increase the abundance of Primordial Black Holes (PBHs) formed by many orders of magnitude. The power spectrum created by the inflaton can be as little as 10-4 during a phase of Ultra Slow-Roll and still form a cosmologically relevant number of PBHs. We conclude that the presence of spectator fields, which very generically will alter the end of inflation, is an effect that cannot be ignored in realistic models of PBH formation.

Disentangling the Black Hole Mass Spectrum with Photometric Microlensing Surveys

From the formation mechanisms of stars and compact objects to nuclear physics, modern astronomy frequently leverages surveys to understand populations of objects to answer fundamental questions. The population of dark and isolated compact objects in the Galaxy contains critical information related to many of these topics, but is only practically accessible via gravitational microlensing. However, photometric microlensing observables are degenerate for different types of lenses, and one can seldom classify an event as involving either a compact object or stellar lens on its own. To address this difficulty, we apply a Bayesian framework that treats lens type probabilistically and jointly with a lens population model. This method allows lens population characteristics to be inferred despite intrinsic uncertainty in the lens class of any single event. We investigate this method’s effectiveness on a simulated ground-based photometric survey in the context of characterizing a hypothetical population of primordial black holes (PBHs) with an average mass of 30M ⊙. On simulated data, our method outperforms current black hole (BH) lens identification pipelines and characterizes different subpopulations of lenses while jointly constraining the PBH contribution to dark matter to ≈25%. Key to robust inference, our method can marginalize over population model uncertainty. We find the lower mass cutoff for stellar origin BHs, a key observable in understanding the BH mass gap, particularly difficult to infer in our simulations. This work lays the foundation for cutting-edge PBH abundance constraints to be extracted from current photometric microlensing surveys.

Primordial Black Hole Merger Rate in f(R) Gravity

Primordial black holes (PBHs) are known as one of the potential candidates for dark matter. They are expected to have formed due to the direct gravitational collapse of density fluctuations in the early Universe. In this regard, examining the merger rate of PBHs within modified theories of gravity can offer a deeper insight into their abundance. In this work, we delve into the calculation of the merger rate of PBHs within the theoretical framework of f(R) gravity. Our analysis reveals an enhancement in the merger rate of PBHs compared to that obtained from general relativity. Additionally, modulating the field strength f R0 induces shifts in the PBH merger rate, presenting a potential observational signature of modified gravity. We also explore the upper bounds on the abundance of PBHs obtained from f(R) gravity models by comparing the results with gravitational-wave and observational data. The results indicate that in certain regions not excluded by benchmarking data, the parameter space for these upper bounds may be considered reliable.

Recent Gravitational Wave Observation by Pulsar Timing Arrays and Primordial Black Holes: The Importance of Non-Gaussianities.

We study whether the signal seen by pulsar timing arrays (PTAs) may originate from gravitational waves (GWs) induced by large primordial perturbations. Such perturbations may be accompanied by a sizable primordial black hole (PBH) abundance. We improve existing analyses and show that PBH overproduction disfavors Gaussian scenarios for scalar-induced GWs at 2σ and single-field inflationary scenarios, accounting for non-Gaussianity, at 3σ as the explanation of the most constraining NANOGrav 15-year data. This tension can be relaxed in models where non-Gaussianities suppress the PBH abundance. On the flip side, the PTA data does not constrain the abundance of PBHs.

Primordial black holes as near infrared background sources

Abstract The near infrared background (NIRB) is the collective light from unresolved sources observed in the band 1–10 $\rm{\mu m}$. The measured NIRB angular power spectrum on angular scales θ ≳ 1 arcmin exceeds by roughly two order of magnitudes predictions from known galaxy populations. The nature of the sources producing these fluctuations is still unknown. Here we test primordial black holes (PBHs) as sources of the NIRB excess. Considering PBHs as a cold dark matter (DM) component, we model the emission of gas accreting onto PBHs in a cosmological framework. We account for both accretion in the intergalactic medium (IGM) and in DM haloes. We self consistently derive the IGM temperature evolution, considering ionization and heating due to X-ray emission from PBHs. Besides ΛCDM, we consider a model that accounts for the modification of the linear matter power spectrum due to the presence of PBHs; we also explore two PBH mass distributions, i.e. a δ-function and a lognormal distribution. For each model, we compute the mean intensity and the angular power spectrum of the NIRB produced by PBHs with mass 1–$10^3~\rm M_{\odot}$. In the limiting case in which the entirety of DM is made of PBHs, the PBH emission contributes &amp;lt;1 per cent to the observed NIRB fluctuations. This value decreases to &amp;lt;0.1 per cent if current constraints on the abundance of PBHs are taken into account. We conclude that PBHs are ruled out as substantial contributors to the NIRB.

On the feasibility of primordial black hole abundance constraints using lensing parallax of GRBs

ABSTRACT Primordial black holes, which could have formed during the early Universe through overdensities in primordial density fluctuations during inflation, are potential candidates for dark matter. We explore the use of lensing parallax of gamma-ray bursts (GRBs), which results in different fluxes being observed from two different vantage points, in order to probe the abundance of primordial black holes in the unexplored window within the mass range 10−15 to 10−11 $\mathrm{ {M}_\odot}$. We derive the optical depth for the lensing of GRBs with a distribution of source properties and realistic detector sensitivities. We comment on the ability of the proposed Indian twin satellite mission Daksha in its low Earth orbit to conduct this experiment. If the two Daksha satellites observe 10 000 GRBs simultaneously and the entirety of dark matter is made up of 10−15 to 10−12 $\mathrm{ {M}_\odot}$ black holes, Daksha will detect non-zero lensing events with a probability ranging from 80 to 50 per cent at the bin edges, respectively. Non-detections will not conclusively rule out primordial black holes as dark matter in this mass range. However, we show that meaningful constraints can be obtained in such a case if the two satellites are separated by at least the Earth–Moon distance.

Highly asymmetric probability distribution from a finite-width upward step during inflation

We study a single-field inflation model in which the inflaton potential has an upward step between two slow-roll regimes by taking into account the finite width of the step. We calculate the probability distribution function (PDF) of the curvature perturbation P[ℛ] using the δN formalism. The PDF has an exponential-tail only for positive ℛ whose slope depends on the step width. We find that the tail may have a significant impact on the estimation of the primordial black hole abundance. We also show that the PDF P[ℛ] becomes highly asymmetric on a particular scale exiting the horizon before the step, at which the curvature power spectrum has a dip. This asymmetric PDF may leave an interesting signature in the large scale structure such as voids.

Constraints on primordial black holes in the mixed dark matter scenarios using the ratio (3He+D)/H\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm (^3{He}+D)/H$$\\end{document}

We derive the upper limit on the dark matter (DM) fraction in primordial black holes (PBHs) in the mixed DM scenarios. In this scenarios, a PBH can accrete weakly interacting massive particles (WIMPs) to form a ultracompact minihalo (UCMH) with a density profile of ρDM(r)∼r-9/4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho _{\ extrm{DM}}(r)\\sim r^{-9/4}$$\\end{document}. The energy released from UCMHs due to dark matter annihilation has influence on the photodissociation of 4He\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{4}{\ extrm{He}}$$\\end{document}, producing the 3He\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3}{\ extrm{He}}$$\\end{document} and the D. By requiring that the ratio (3He+D)/H\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(^3\ ext {He}+\ ext {D})/\ ext {H}$$\\end{document} caused by UCMHs does not exceed the measured value, we derive the upper limit on the dark matter fraction in PBHs. For the canonical value of DM thermally averaged annihilation cross section σv=3×10-26cm3s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left<\\sigma v\\right>=3\ imes 10^{-26}\ ext {cm}^{3}\\,\ ext {s}^{-1}$$\\end{document}, we find that the upper limit is fPBH<0.35(0.75)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{\ extrm{PBH}} < 0.35(0.75)$$\\end{document} for DM mass mχ=1(10)GeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_{\\chi }=1(10)~ \ ext {GeV}$$\\end{document}. Compared with other limits obtained by different astronomical measurements, although our limit is not the strongest, we provide a different way of constraining the cosmological abundance of PBHs.

The primordial black holes that disappeared: connections to dark matter and MHz-GHz gravitational Waves

In the post-LIGO era, there has been a lot of focus on primordial black holes (PBHs) heavier than ∼ 1015g as potential dark matter (DM) candidates. We point out that the branch of the PBH family that disappeared — PBHs lighter than ∼ 109g that ostensibly Hawking evaporated away in the early Universe — also constitute an interesting frontier for DM physics. Hawking evaporation itself serves as a portal through which such PBHs can illuminate new physics, for example by emitting dark sector particles. Taking a simple DM scalar singlet model as a template, we compute the abundance and mass of PBHs that could have provided, by Hawking evaporation, the correct DM relic density. We consider two classes of such PBHs: those originating from curvature perturbations generated by inflation, and those originating from false vacuum collapse during a first-order phase transition. For PBHs of both origins we compute the gravitational wave (GW) signals emanating from their formation stage: from second-order effects in the case of curvature perturbations, and from sound waves in the case of phase transitions. The GW signals have peak frequencies in the MHz-GHz range typical of such light PBHs. We compute the strength of such GWs compatible with the observed DM relic density, and find that the GW signal morphology can in principle allow one to distinguish between the two PBH formation histories.

How well do we know the primordial black hole abundance: The crucial role of nonlinearities when approaching the horizon

How well do we know the primordial black hole abundance: The crucial role of nonlinearities when approaching the horizon

Primordial black holes from strong first-order phase transitions

We study the formation of primordial black holes (PBHs) in strongly super-cooled first-order phase transitions. The mechanism is based on the presence of remnants dominated by the false vacuum that scale slower with the expansion of the Universe than their surroundings where this energy was already converted into radiation. We compute the PBH formation from these remnants including the contribution from the false vacuum and the bubble walls, by estimating the collapse using the hoop conjecture and by considering both regions collapsing immediately when entering the horizon and sub-horizon regions that collapse as their compactness grows. We show that for exponential bubble nucleation rate, Γ ∝ eβt, the primordial black hole formation implies β/H ≳ 3.8, where H denotes the Hubble rate, if the potential energy of the false vacuum is ∆V ≲ (1012 GeV)4, as otherwise a too large abundance of long-lived PBHs forms. The observed dark matter abundance can be formed in asteroid mass PBHs if β/H ≃ 3.8 and 105 GeV ≲ ∆V1/4 ≲ 108 GeV. Finally, we consider also the effect of the second order correction to the exponential nucleation rate showing that the PBH abundance is mainly determined by the average radius of the true vacuum bubbles.

Tail diversity from inflation

The tail of the distribution of primordial fluctuations (corresponding to the likelihood of realization of large fluctuations) is of interest, from both theoretical and observational perspectives. In particular, it is relevant for the accurate evaluation of the primordial black hole (PBH) abundance. In this paper, we first analyze the non-perturbative δN formalism as a method to non-perturbatively estimate the probability distribution function (PDF) of primordial fluctuations, discuss its underlying assumptions and deal with several subtleties that may arise as a result of considering large fluctuations. Next, we employ the method to study several non-attractor single-field inflationary models as the simplest examples that may lead to the abundant production of PBHs. We conclude that the Gaussian extrapolation from linear perturbation theory may fail drastically to predict the likelihood of large fluctuations. Specifically, we show that a truncation of the tail, a power-law tail, a double-exponential tail, and a doubly peaked distribution can all be realized for the curvature perturbation in the single-field non-attractor models of inflation. We thus show that there is a diverse zoo of possible tails from inflation so that a model-dependent, non-perturbative study of the distribution of the primordial fluctuations seems inevitable concerning PBH abundance.

Constraints on the Abundance of Primordial Black Holes from X-Ray Quasar Microlensing Observations: Substellar to Planetary Mass Range

We use X-ray observations of quasar microlensing (sensitive to smaller compact objects than in the optical) to study the possible presence of a population of low mass black holes (BHs; from ∼10−3 M ⊙ to 10−1 M ⊙) in lens galaxies. We compare these observations with microlensing magnification simulations of a mixed population of stars and BHs plus a smooth matter component. We estimate the individual mass fractions of both stars and BHs for three different BH masses in the range of substellar to planetary masses. Our Bayesian analysis indicates that the contribution of BHs is negligible in the substellar mass range but that a population of BHs of planetary mass (M ≲ 10−3 M ⊙) could pass unnoticed to X-ray microlensing. We provide new upper limits to the contribution of BHs to the fraction of dark matter based on both, the quasar microlensing data in the X-ray band, and our previous estimates in the optical of intermediate-mass BHs with an additional upper limit at M = 3M ⊙.

511 keV line and primordial black holes from first-order phase transitions

511 keV gamma-ray excess from the Galactic center is a long lasting anomaly without satisfying astrophysical explanation. Hawking evaporation of hypothetical primordial black hole (PBH) with mass 1.0 × 10-17 ≲ M PBH/M ⊙ ≲ 8.0 × 10-17 and fractional abundance 10-3 ≲ f PBH ≲ 1.0, gives rise substantial non-relativistic electrons/positrons annihilating into diphoton, well reproduces the 511 keV line. However, it is obscure of the mechanism behind to form PBH with meteoritical mass in the early Universe. In this work, we investigated the production mechanism of PBHs through a cosmological first-order phase transition induced by quartic effective thermal potential via a scalar field in dark sector. We found the phase transition with vacuum energy, 𝒪(1) ≲ B 1/4/MeV ≲ 𝒪 (100), produces the desired monochromatic PBH mass and abundance fraction. Correlated signatures of gravitational wave and extragalactic gamma-ray, respectively coming from phase transition and black hole evaporation, are within μAres and AMEGO/e-ASTROGAM/COSI/XGIS-THESUS projected sensitivities. Finally, we include the PBH mass function from FOPT and found it can not improve the explanation to 511 keV excess.

Primordial black holes from single-field inflation: a fine-tuning audit

All single-field inflationary models invoke varying degrees of tuning in order to account for cosmological observations. Mechanisms that generate primordial black holes (PBHs) from enhancement of primordial power at small scales posit inflationary potentials that transiently break scale invariance and possibly adiabaticity over a range of modes. This requires additional tuning on top of that required to account for observations at scales probed by cosmic microwave background (CMB) anisotropies. In this paper we study the parametric dependence of various single-field models of inflation that enhance power at small scales and quantify the degree to which coefficients in the model construction have to be tuned in order for certain observables to lie within specified ranges. We find significant tuning: changing the parameters of the potentials by between one part in a hundred and one part in 108 (depending on the model) is enough to change the power spectrum peak amplitude by an order one factor. The fine-tuning of the PBH abundance is larger still by 1–2 orders of magnitude. We highlight the challenges imposed by this tuning on any given model construction. Furthermore, polynomial potentials appear to require significant additional fine-tuning to also match the CMB observations.

Growth of curvature perturbations for PBH formation & detectable GWs in non-minimal curvaton scenario revisited

We revisit the growth of curvature perturbations in non-minimal curvaton scenario with a non-trivial field metric λ(ϕ) where ϕ is an inflaton field, and incorporate the effect from the non-uniform onset of curvaton's oscillation in terms of an axion-like potential. The field metric λ(ϕ) plays a central role in the enhancement of curvaton field perturbation δχ, serving as an effective friction term which can be either positive or negative, depending on the first derivative λ ,ϕ . Our analysis reveals that δχ undergoes the superhorizon growth when the condition η eff ≡ -2 √2ϵ M Pl λ ,ϕ /λ < -3 is satisfied. This is analogous to the mechanism responsible for the amplification of curvature perturbations in the context of ultra-slow-roll inflation, namely the growing modes dominate curvature perturbations. As a case study, we examine the impact of a Gaussian dip in λ(ϕ) and conduct a thorough investigation of both the analytical and numerical aspects of the inflationary dynamics. Our findings indicate that the enhancement of curvaton perturbations during inflation is not solely determined by the depth of the dip in λ(ϕ). Rather, the first derivative λ ,ϕ also plays a significant role, a feature that has not been previously highlighted in the literature. Utilizing the δ𝒩 formalism, we derive analytical expressions for both the final curvature power spectrum and the non-linear parameter f NL in terms of an axion-like curvaton's potential leading to the non-uniform curvaton's oscillation. Additionally, the resulting primordial black hole abundance and scalar-induced gravitational waves are calculated, which provide observational windows for PBHs.