Closed-form mode functions and power spectrum for a two-field inflation model with arbitrary coupling λ and isocurvature mass μ, including the previously difficult strong-coupling regime.
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Density Perturbations and Black Hole Formation in Hybrid Inflation
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abstract
We investigate the recently proposed hybrid inflation models with two stages of inflation. We show that quantum fluctuations at the time corresponding to the phase transition between the two inflationary stages can trigger the formation of a large number of inflating topological defects. In order to study density perturbations in these models we develop a new method to calculate density perturbations in a system of two scalar fields. We show that density perturbations in hybrid inflation models of the new type can be very large on the scale corresponding to the phase transition. The resulting density inhomogeneities lead to a copious production of black holes. This could be an argument against hybrid inflation models with two stages of inflation. However, we find a class of models where this problem can be easily avoided. The number of black holes produced in these models can be made extremely small, but in general it could be sufficiently large to have important cosmological and astrophysical implications. In particular, for certain values of parameters these black holes may constitute the dark matter in the universe. It is also possible to have hybrid models with two stages of inflation where the black hole production is not suppressed, but where the typical masses of the black holes are very small. Such models lead to a completely different thermal history of the universe, where post-inflationary reheating occurs via black hole evaporation.
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representative citing papers
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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.
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.
Lattice simulations of bumpy axion U(1) inflation in the strong backreaction regime generate curvature perturbations large enough for primordial black holes to comprise all dark matter.
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Torsion-induced fermion condensate produces hybrid inflation with axial-chemical-potential waterfall, Q-ball PBH seeds, and parity-violating signatures in Chern-Simons gravity.
For monochromatic primordial black holes, the low-frequency scalar-induced gravitational-wave peak and the high-frequency binary-merger ISCO frequency are linked by fISCO ≈ 3.4×10^20 Hz × (fSIGW/Hz)^2.
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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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The Magnetic Origin of Primordial Black Holes: Ultralight PBHs and Secondary GWs
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The End of the First Act: Spectral Running, Interacting Dark Radiation, and the Hubble Tension in Light of ACT DR6 Data
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Fermion Condensate Inflation, Dynamical Waterfall Mechanism and Primordial Black Holes
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Gravitational Waves from Primordial Black Holes: Connecting Low-Frequency Scalar-Induced Signatures to High-Frequency Binary Mergers
For monochromatic primordial black holes, the low-frequency scalar-induced gravitational-wave peak and the high-frequency binary-merger ISCO frequency are linked by fISCO ≈ 3.4×10^20 Hz × (fSIGW/Hz)^2.
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Primordial black hole formation in bulk-viscous cosmology
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Exploring Gravitational Wave Signatures Due to Primordial Non-gaussianity and Large Scale Structure Using SKAO
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