The first search for scalar-induced gravitational waves via pulsar parameter drifts yields f_PBH < 10^{-10} (95% CL) for PBH masses 0.3 to 4e4 solar masses, strongly disfavoring a primordial black hole origin for LVK binary black holes.
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Constraints on Primordial Black Holes
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abstract
We update the constraints on the fraction of the Universe that may have gone into primordial black holes (PBHs) over the mass range $10^{-5}\text{--}10^{50}$ g. Those smaller than $\sim 10^{15}$ g would have evaporated by now due to Hawking radiation, so their abundance at formation is constrained by the effects of evaporated particles on big bang nucleosynthesis, the cosmic microwave background (CMB), the Galactic and extragalactic $\gamma$-ray and cosmic ray backgrounds and the possible generation of stable Planck mass relics. PBHs larger than $\sim 10^{15}$ g are subject to a variety of constraints associated with gravitational lensing, dynamical effects, influence on large-scale structure, accretion and gravitational waves. We discuss the constraints on both the initial collapse fraction and the current fraction of the CDM in PBHs at each mass scale but stress that many of the constraints are associated with observational or theoretical uncertainties. We also consider indirect constraints associated with the amplitude of the primordial density fluctuations, such as second-order tensor perturbations and $\mu$-distortions arising from the effect of acoustic reheating on the CMB, if PBHs are created from the high-$\sigma$ peaks of nearly Gaussian fluctuations. Finally we discuss how the constraints are modified if the PBHs have an extended mass function, this being relevant if PBHs provide some combination of the dark matter, the LIGO/Virgo coalescences and the seeds for cosmic structure. Even if PBHs make a small contribution to the dark matter, they could play an important cosmological role and provide a unique probe of the early Universe.
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Vector modes from primordial magnetic fields remain constant in a kination epoch and source second-order curvature perturbations scaling as P_R(k) ∝ k^{-5}, sufficient for PBH dark matter abundance in a Ratra-type magnetogenesis model.
PBH dark matter spans all naturalness tiers, with some mechanisms as natural as WIMPs or freeze-in particles, determined by abundance map structure rather than candidate type.
A warped 5D geometry with hidden-sector accretion produces growing Schwarzschild/Vaidya black-hole seeds on our brane via a common horizon intersection.
Self-consistent spherical accretion simulations show cooling-enhanced growth of PBHs with radiative efficiency ~10^{-2} in the bremsstrahlung regime, yielding a critical seed mass of ~10^{-16} M_sun to consume a solar-mass star in a Hubble time.
Non-singular gravity with regulator ℓ induces a PBH mass gap ~c²ℓ/G and a stronger Carr criterion δ_H > 2GM_gap/R_H - 1 when R_H ~ ℓ.
Accounting for the minimal mass spread of primordial black holes from gravitational collapse suppresses the Poltergeist GW background to the level of generic scalar-induced signals and reopens ultra-light PBH parameter space.
A semiclassical tunneling model shows that two-field ultralight DM halos have stability bounds that can be relaxed for some density-mass ratios but become more stringent across much of the parameter space compared to single-field cases.
Full numerical N-body treatment is required for reliable gravitational wave predictions from nonspherical collapse in early matter-dominated eras, with resulting spectra mappable to detector sensitivities via horizon mass and reheating temperature.
A quenched-disorder approach with Schwinger-Keldysh path integrals produces an averaged density matrix for gravitational waves that separates phase-suppressing exponential terms from oscillatory corrections to coherent propagation.
Stupendously large black holes cast shadows on the CMB that rule out masses above 10^17 solar masses within the last scattering surface and limit their density parameter to below 10^-5 for masses 10^15 to 10^18 solar masses.
Ratio-Filter Dechirping converts gravitational-wave matched filtering from a memory-bound FFT into a cache-efficient FIR convolution, delivering a measured 8x speedup in the core loop.
Nonlinear long-wavelength solutions are constructed for cosmological perturbations in non-adiabatic multi-fluid systems, admitting adiabatic and entropy modes at leading order via ADM and gradient expansion.
Strongly interacting dark matter described by a first-principles G2 gauge-theory equation of state can be mixed into neutron stars while remaining compatible with current observational constraints.
Shape dispersion around the average peak profile is a genuine statistical ingredient: rare deformed curvature profiles can dominate primordial black hole formation when the power spectrum is broad or non-Gaussianity is negative.
Bumblebee gravity enhances primordial black hole abundance through three mechanisms, but the model harbors a ghost instability and a tachyonic instability that make it cosmologically unviable.
BHL-type post-recombination accretion can raise late three-body PBH merger rates enough for TianQin detections at f~10^{-6} and for LVK limits to bound delayed virialization.
Scaling monopoles generate PBHs via stochastic overdensities and GWs with correlated spectra, potentially with magnetically charged PBHs as a signature if the scaling ends via gauge boson mass.
Periodic warm inflation imprints one log-periodic feature on the curvature spectrum that saturates asteroid-mass PBHs, generates dual-band GW backgrounds, and offsets the bispectrum phase by a quarter cycle fixed by spectral running.
Curvaton self-interactions in non-quadratic potentials produce a local non-Gaussian map that enables supermassive primordial black hole formation at peak amplitudes of order 10^{-5} while remaining consistent with μ-distortion bounds.
O(100–10^5) light string axions enhance PBH spin-up during Hawking evaporation, boosting superradiant dark-matter cloud efficiency and expanding the micro-boson-star parameter space while contributing negligibly to ΔN_eff.
Monte Carlo and ML surrogate framework projects PTA sensitivity to compact DM substructures and shows SGWB weakens it, with only Shapiro searches retaining sensitivity in optimistic cases.
Asteroid-mass primordial black holes induce a Riemann tidal splitting of the 2P_{3/2} hydrogen state, turning the 9.9 GHz line into a ~2 GHz bandwidth gravitational spectral radio forest in H II regions with accretion-enhanced emission measure.
Hotspots around light primordial black holes cool faster in an expanding universe following T_plt ∝ t^{-11/15} and vanish completely in finite time, unlike everlasting hotspots in flat spacetime.
citing papers explorer
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Constraints on the Primordial Black Hole Abundance using Pulsar Parameter Drifts
The first search for scalar-induced gravitational waves via pulsar parameter drifts yields f_PBH < 10^{-10} (95% CL) for PBH masses 0.3 to 4e4 solar masses, strongly disfavoring a primordial black hole origin for LVK binary black holes.
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Primordial Black Holes from Vector-Induced Curvature Perturbations Sourced by Primordial Magnetic Fields
Vector modes from primordial magnetic fields remain constant in a kination epoch and source second-order curvature perturbations scaling as P_R(k) ∝ k^{-5}, sufficient for PBH dark matter abundance in a Ratra-type magnetogenesis model.
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Are Primordial Black Holes a Natural Dark Matter Candidate?
PBH dark matter spans all naturalness tiers, with some mechanisms as natural as WIMPs or freeze-in particles, determined by abundance map structure rather than candidate type.
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Hidden-sector accretion and warped black-string seeds for high-redshift supermassive black holes
A warped 5D geometry with hidden-sector accretion produces growing Schwarzschild/Vaidya black-hole seeds on our brane via a common horizon intersection.
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Accretion of Primordial Black Holes in Stellar Interiors
Self-consistent spherical accretion simulations show cooling-enhanced growth of PBHs with radiative efficiency ~10^{-2} in the bremsstrahlung regime, yielding a critical seed mass of ~10^{-16} M_sun to consume a solar-mass star in a Hubble time.
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Carr criterion and mass gaps in non-singular primordial black hole formation
Non-singular gravity with regulator ℓ induces a PBH mass gap ~c²ℓ/G and a stronger Carr criterion δ_H > 2GM_gap/R_H - 1 when R_H ~ ℓ.
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Gravitational Waves from Black Hole Reheating: The Scalar-Induced Component
Accounting for the minimal mass spread of primordial black holes from gravitational collapse suppresses the Poltergeist GW background to the level of generic scalar-induced signals and reopens ultra-light PBH parameter space.
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Tunneling and tidal stripping in multifield ultralight dark matter halos
A semiclassical tunneling model shows that two-field ultralight DM halos have stability bounds that can be relaxed for some density-mass ratios but become more stringent across much of the parameter space compared to single-field cases.
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Gravitational wave emission from nonspherical collapse in an early matter-dominated era using N-body simulations
Full numerical N-body treatment is required for reliable gravitational wave predictions from nonspherical collapse in early matter-dominated eras, with resulting spectra mappable to detector sensitivities via horizon mass and reheating temperature.
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Gravitational-wave lensing beyond rays: a disordered-system approach
A quenched-disorder approach with Schwinger-Keldysh path integrals produces an averaged density matrix for gravitational waves that separates phase-suppressing exponential terms from oscillatory corrections to coherent propagation.
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Shadows of Giants: Constraints on Stupendously Large Black Holes from Negative Sources against the Cosmic Microwave Background
Stupendously large black holes cast shadows on the CMB that rule out masses above 10^17 solar masses within the last scattering surface and limit their density parameter to below 10^-5 for masses 10^15 to 10^18 solar masses.
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Beyond FINDCHIRP: Breaking the memory wall and optimal FFTs for Gravitational-Wave Matched-Filter Searches with Ratio-Filter Dechirping
Ratio-Filter Dechirping converts gravitational-wave matched filtering from a memory-bound FFT into a cache-efficient FIR convolution, delivering a measured 8x speedup in the core loop.
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Cosmological long-wavelength solutions in non-adiabatic multi-fluid systems
Nonlinear long-wavelength solutions are constructed for cosmological perturbations in non-adiabatic multi-fluid systems, admitting adiabatic and entropy modes at leading order via ADM and gradient expansion.
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Strongly Interacting Dark Matter admixed Neutron Stars
Strongly interacting dark matter described by a first-principles G2 gauge-theory equation of state can be mixed into neutron stars while remaining compatible with current observational constraints.
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The statistics of curvature-profile dispersion in primordial black hole formation
Shape dispersion around the average peak profile is a genuine statistical ingredient: rare deformed curvature profiles can dominate primordial black hole formation when the power spectrum is broad or non-Gaussianity is negative.
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Primordial black hole in Lorentz-violating theories: Insights from Bumblebee gravity
Bumblebee gravity enhances primordial black hole abundance through three mechanisms, but the model harbors a ghost instability and a tachyonic instability that make it cosmologically unviable.
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Effect of post-recombination accretion on primordial binary black hole mergers within virialized dark matter halos
BHL-type post-recombination accretion can raise late three-body PBH merger rates enough for TianQin detections at f~10^{-6} and for LVK limits to bound delayed virialization.
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PBHs and GWs from Scaling Monopoles
Scaling monopoles generate PBHs via stochastic overdensities and GWs with correlated spectra, potentially with magnetically charged PBHs as a signature if the scaling ends via gauge boson mass.
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One Feature, Three Clocks: Phase-Locked Gravitational Waves, Primordial Black Holes, and Non-Gaussianity from Periodic Warm Inflation
Periodic warm inflation imprints one log-periodic feature on the curvature spectrum that saturates asteroid-mass PBHs, generates dual-band GW backgrounds, and offsets the bispectrum phase by a quarter cycle fixed by spectral running.
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Memoirs of the curvaton: non-perturbative non-Gaussianity and supermassive primordial black holes
Curvaton self-interactions in non-quadratic potentials produce a local non-Gaussian map that enables supermassive primordial black hole formation at peak amplitudes of order 10^{-5} while remaining consistent with μ-distortion bounds.
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String Axiverse Enhancement of Superradiant Dark Matter Production
O(100–10^5) light string axions enhance PBH spin-up during Hawking evaporation, boosting superradiant dark-matter cloud efficiency and expanding the micro-boson-star parameter space while contributing negligibly to ΔN_eff.
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Projecting the ultimate pulsar timing sensitivity to dark matter substructure in a stochastic gravitational wave background
Monte Carlo and ML surrogate framework projects PTA sensitivity to compact DM substructures and shows SGWB weakens it, with only Shapiro searches retaining sensitivity in optimistic cases.
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The Gravitational Spectral Radio Forest: A Signature of Primordial Black Holes
Asteroid-mass primordial black holes induce a Riemann tidal splitting of the 2P_{3/2} hydrogen state, turning the 9.9 GHz line into a ~2 GHz bandwidth gravitational spectral radio forest in H II regions with accretion-enhanced emission measure.
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Primordial Black Hole Hotspots Beyond Flat Spacetime
Hotspots around light primordial black holes cool faster in an expanding universe following T_plt ∝ t^{-11/15} and vanish completely in finite time, unlike everlasting hotspots in flat spacetime.
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Nonperturbative stochastic inflation in perturbative dynamical background
Derives stochastic equations from Schwinger-Keldysh formalism that include quantum diffusion and classical metric perturbations for non-perturbative ultra-slow-roll inflation, validated on Starobinsky and critical Higgs models.
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High-energy neutrino constraints on primordial black holes as dark matter
High-energy neutrino telescopes constrain sub-asteroid mass primordial black holes with extended mass functions as dark matter, yielding limits slightly weaker than but independent of gamma-ray bounds.
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Smoluchowski Coagulation Equation and the Evolution of Primordial Black Hole Clusters
Monte Carlo solutions of the Smoluchowski equation for PBH clusters yield finite runaway timescales and evolving mass distributions that form high-redshift SMBHs, shortened further by mass segregation.
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Primordial black holes and the velocity acoustic oscillations features in 21 cm signals from the cosmic Dark Ages
Primordial black holes generate up to 30% amplitude VAO wiggles in 21 cm signals from the Dark Ages at redshifts 20-40 even at dark matter fractions as low as 10^-13.
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Constraining memory-burdened primordial black holes with graviton-photon conversion and binary mergers
Derives gamma-ray upper limits on memory-burdened PBH dark matter abundance using graviton-photon conversion during recombination and merger-induced semiclassical evaporation, excluding mass windows 7.5e5-4.4e7 g and below 2.2e11 g under stated assumptions.
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GW231123: A Possible Primordial Black Hole Origin
GW231123's masses and high spins are consistent with primordial black holes that accreted mass and angular momentum in the early universe within the standard PBH framework.
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Isotropy, anisotropies and non-Gaussianity in the scalar-induced gravitational-wave background: diagrammatic approach for primordial non-Gaussianity up to arbitrary order
Extends diagrammatic approach for scalar-induced gravitational waves to arbitrary-order local PNG, deriving semi-analytic spectra for energy density, anisotropies, bispectrum and trispectrum up to quartic terms.
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Cancellation of one-loop time dependence in superhorizon curvature perturbations from all scales
One-loop time dependence in superhorizon curvature perturbations cancels when all-scale contributions and boundary terms are included consistently via the δN formalism.
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A Solar-System Window for Hidden Stellar Companions
The paper builds an illustrative mass-distance window for hidden-brane companions and finds overlap with the minimum mass of a QCD-scaled hidden star at the upper end of the allowed range.
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Graviton Floor
Photon-to-graviton conversion in blazar jets dominates a new graviton background that sets a floor for high-frequency GW detectors, analogous to the neutrino floor.
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Universal Suppression of Gravitational Waves from Black Hole Evaporation Dynamics
Black hole populations with finite-width mass distributions exhibit universal late-time evaporation-driven evolution that produces characteristic power-law suppression of induced gravitational waves, directly linking the asymptotic GW spectrum to the evaporation law.
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Primordial Black Holes from Slow Phase Transitions with Delayed Reheating: A Peak-Theory Approach
PBH production from slow phase transitions with delayed reheating is modeled via peak theory and Monte Carlo simulations, showing extreme sensitivity to reheating efficiency and potential to explain all dark matter.
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A New Origin of the Big Bang from Dark-Sector-Induced Vacuum Decay and Its Gravitational-Wave Signal
A model in which inflaton energy goes exclusively to a dark sector, delaying SM thermalization until a false-vacuum decay produces a GW background with present-day Omega_GW up to 3e-8.
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$\tt BlackHawk$ $\tt v3.0$: Hawking Radiation from Regular Black Holes
BlackHawk v3.0 adds Hawking temperatures and greybody factors for multiple regular black hole metrics to an existing public code via numerical routines.
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Signatures of loop quantum gravity in primordial black hole cosmologies
PBH masses near 10^3 kg allow Hawking evaporation to reheat the universe while Planckian remnants comprise all present-day DM without fine-tuning initial abundance, yielding testable GW signals.
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Electromagnetic Signatures From Primordial Black Holes in the Solar System
Calculations indicate AMEGO-X could detect PBH transits within 0.1 AU while HAWC and LHAASO could observe explosions out to 0.1-0.5 pc, with future events at ~1000 AU potentially producing measurable electromagnetic signals unlike the 2023 KM3NeT neutrino candidate.
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Subcritical bubble prehistory in weak first-order phase transition
In weak first-order phase transitions, subcritical bubbles reach percent-level volume fractions before critical nucleation when phases are nearly degenerate at Tn, invalidating the homogeneous-background assumption for points satisfying log10 f̂_ξ(Tn) ≃ -1.95.
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Primordial black holes in excursion set theory: Formation probabilities, mass functions, and window functions
In excursion set theory with colored noises, the low-mass tail of the PBH mass function differs from Carr's formula because correlated noises end the degeneracy of formation probabilities, though Carr's formula remains practical near the characteristic mass for smooth Fourier-space window functions.
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Inflaton Accretion onto Primordial Black Holes During Reheating
Inflaton accretion during reheating drives non-linear PBH mass growth that extends lifetimes and amplifies emitted SGWB by multiple orders of magnitude.
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Memory burden effect of regular primordial black holes
Combining regular black hole metrics with memory burden suppresses evaporation and opens a 10^6-10^8 g PBH mass window that can comprise all dark matter.
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Primordial Black Hole from Tensor-induced Density Fluctuation: First-order Phase Transitions and Domain Walls
Tensor perturbations from FOPT and domain-wall sources are claimed to induce second-order scalar perturbations large enough to form primordial black holes, potentially all of the dark matter.
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The Magnetic Origin of Primordial Black Holes: Ultralight PBHs and Secondary GWs
Inflationary magnetic fields induce curvature perturbations that form ultralight PBHs, generating a stochastic GW background with model-specific features.
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Reviving primordial black hole formation in slow first-order phase transitions
Slow reheating after a supercooled first-order phase transition allows an early matter-dominated era in which small curvature perturbations grow sufficiently to form primordial black holes.
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Primordial black hole dark matter from axion inflation
PBHs generated by axion inflation with gauge-field coupling can comprise all dark matter in the asteroidal mass range while producing a LISA-measurable stochastic GW background.
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Inflation driven by repulsive-like primordial black holes
Repulsive-like primordial black holes in the Swiss-cheese framework produce quasi-de Sitter expansion, enabling inflation with evaporation reheating and acting as early dark energy for certain masses and densities.
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Purely quadratic non-Gaussianity from tachyonic instability: Primordial black holes and scalar-induced gravitational waves
For tachyonic models with ζ=A(φ²−σ²), the PBH abundance is exponentially set by the correlation ρ between field and radial gradient; narrow spectra drive ρ→−1 and suppress PBH formation without killing the induced GW signal.