Computes the dimensionless spin parameter s = J/(G_N M^2) of false vacuum bubbles from density and velocity perturbations in FOPTs, yielding values from O(10^{-5}) to O(10) and a scaling relation with FOPT timescale, wall velocity, and temperature ratio.
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Threshold of primordial black hole formation
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abstract
Based on a physical argument, we derive a new analytic formula for the amplitude of density perturbation at the threshold of primordial black hole formation in the universe dominated by a perfect fluid with the equation of state $p=w\rho c^{2}$ for $w\ge 0$. The formula gives $\delta^{\rm UH}_{H c}=\sin^{2}[\pi \sqrt{w}/(1+3w)]$ and $\tilde{\delta}_{c}=[3(1+w)/(5+3w)]\sin^{2}[\pi\sqrt{w}/(1+3w)]$, where $\delta^{\rm UH}_{H c}$ and $\tilde{\delta}_{c}$ are the amplitude of the density perturbation at the horizon crossing time in the uniform Hubble slice and the amplitude measure used in numerical simulations, respectively, while the conventional one gives $\delta^{\rm UH}_{H c}=w$ and $\tilde{\delta}_{c}=3w(1+w)/(5+3w)$. Our formula shows a much better agreement with the result of recent numerical simulations both qualitatively and quantitatively than the conventional formula. For a radiation fluid, our formula gives $\delta^{\rm UH}_{H c}=\sin^{2}(\sqrt{3}\pi/6)\simeq 0.6203$ and $\tilde{\delta}_{c}=(2/3)\sin^{2}(\sqrt{3}\pi/6)\simeq 0.4135$. We also discuss the maximum amplitude and the cosmological implications of the present result.
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background 6representative citing papers
Large initial baryon asymmetry allows Hubble patches to collapse into primordial neutron stars arrested by nuclear pressure, requiring later entropy dilution to match observed Y_B and BBN.
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.
Inflaton accretion during reheating drives non-linear PBH mass growth that extends lifetimes and amplifies emitted SGWB by multiple orders of magnitude.
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.
3D simulations of cosmological first-order phase transitions find density perturbation spectra with k^3 and k^{-1.5} slopes and GW spectra with k^3 and k^{-2}, confirming slow transitions can produce PBHs.
Updated compilation shows PBHs are tightly constrained across 55 orders of magnitude in mass, ruling out dominant dark matter contributions except in narrow windows, with many limits carrying observational uncertainties.
Multi-band GW observations of PBHs can reduce H0 uncertainty to ≲2 km/s/Mpc (conservative) or O(0.1) km/s/Mpc (optimistic) via Fisher forecasts on M_PBH and f_PBH.
CMB data limits the s-wave annihilation cross section of thermal dark matter particles to ≲ 10^{-30} cm³/s scaled by PBH fraction and mass for PBHs heavier than ~10^{-10} solar masses.
Primordial black holes in specific mass ranges could account for some or all dark matter while resolving structure-formation and seed problems in standard cosmology.
A review that unifies analytical expressions for scalar-induced gravitational waves and emphasizes calculations for non-radiation-dominated cosmologies.
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Angular momentum of vacuum bubbles in a first-order phase transition
Computes the dimensionless spin parameter s = J/(G_N M^2) of false vacuum bubbles from density and velocity perturbations in FOPTs, yielding values from O(10^{-5}) to O(10) and a scaling relation with FOPT timescale, wall velocity, and temperature ratio.
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Primordial Neutron Stars
Large initial baryon asymmetry allows Hubble patches to collapse into primordial neutron stars arrested by nuclear pressure, requiring later entropy dilution to match observed Y_B and BBN.
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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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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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Numerical simulations of density perturbation and gravitational wave production from cosmological first-order phase transition
3D simulations of cosmological first-order phase transitions find density perturbation spectra with k^3 and k^{-1.5} slopes and GW spectra with k^3 and k^{-2}, confirming slow transitions can produce PBHs.
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Constraints on Primordial Black Holes
Updated compilation shows PBHs are tightly constrained across 55 orders of magnitude in mass, ruling out dominant dark matter contributions except in narrow windows, with many limits carrying observational uncertainties.
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Precision Analysis for $\boldsymbol{H_0}$ Using Upcoming Multi-band Gravitational Wave Observations
Multi-band GW observations of PBHs can reduce H0 uncertainty to ≲2 km/s/Mpc (conservative) or O(0.1) km/s/Mpc (optimistic) via Fisher forecasts on M_PBH and f_PBH.
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In-depth analysis of the clustering of dark matter particles around primordial black holes. Part III: CMB constraints
CMB data limits the s-wave annihilation cross section of thermal dark matter particles to ≲ 10^{-30} cm³/s scaled by PBH fraction and mass for PBHs heavier than ~10^{-10} solar masses.
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Primordial Black Holes as Dark Matter: Recent Developments
Primordial black holes in specific mass ranges could account for some or all dark matter while resolving structure-formation and seed problems in standard cosmology.
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Scalar induced gravitational waves review
A review that unifies analytical expressions for scalar-induced gravitational waves and emphasizes calculations for non-radiation-dominated cosmologies.