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Evaporating primordial black holes, the string axiverse, and hot dark radiation

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arxiv 2110.13602 v1 pith:EWW7S3VZ submitted 2021-10-26 astro-ph.CO gr-qchep-ph

classification astro-ph.COgr-qchep-ph
keywords emissionnumberpbhsscalarsblackhawkingholeslarge
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

We show that primordial black holes (PBHs) develop non-negligible spins through Hawking emission of the large number of axion-like particles generically present in string theory compactifications. This is because scalars can be emitted in the monopole mode ($l=0$), where no angular momentum is removed from the BH, so a sufficiently large number of scalars can compensate for the spin-down produced by fermion, gauge boson, and graviton emission. The resulting characteristic spin distributions for $10^8$-$10^{12}$ kg PBHs could potentially be measured by future gamma-ray observatories, provided that the PBH abundance is not too small. This yields a unique probe of the total number of light scalars in the fundamental theory, independent of how weakly they interact with known matter. The present local energy density of hot, MeV-TeV, axions produced by this Hawking emission can possibly exceed $\rho_{\rm CMB}$. Evaporation constraints on PBHs are also somewhat weakened.

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Forward citations

Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Hawking emission of massive vector fields by Kerr black holes

    gr-qc 2026-07 conditional novelty 7.0 of 10

    First computation of massive vector (Proca) Hawking emission spectra from Kerr black holes, including polarization-dependent greybody factors, Page functions, and mass-enhanced superradiance up to ~7%.

  2. String Axiverse Enhancement of Superradiant Dark Matter Production

    hep-ph 2026-06 unverdicted novelty 6.0 of 10

    O(100-10^5) string axions enhance PBH superradiance efficiency via increased spin, expanding viable mass-spin regions for micro-boson star dark matter while too many axions cause overly rapid evaporation.

  3. Primordial Black Hole from Tensor-induced Density Fluctuation: First-order Phase Transitions and Domain Walls

    astro-ph.CO 2026-05 unverdicted novelty 6.0 of 10

    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.

  4. $\tt GrayHawk$: A public code for calculating the Gray Body Factors of massless fields around spherically symmetric Black Holes

    gr-qc 2025-02 conditional novelty 6.0 of 10

    A new public Mathematica tool, GrayHawk, computes gray-body factors for massless spin 0, 1/2, 1, and 2 fields around seven spherically symmetric, asymptotically flat black hole metrics.

  5. Complementary Probes of Warped Extra Dimension: Colliders, Gravitational Waves and Primordial Black Holes from Phase Transitions

    hep-ph 2025-02 conditional novelty 6.0 of 10

    In Randall-Sundrum warped extra dimension models, the supercooled radion phase transition can form primordial black holes that account for all of dark matter for IR scales 10 TeV to 10^4 TeV, with correlated gravitati...

  6. Primordial Black Holes (as Dark Matter) from the Supercooled Phase Transitions with Radiative Symmetry Breaking

    hep-ph 2024-12 conditional novelty 6.0 of 10

    Supercooled radiative symmetry breaking phase transitions generically produce primordial black holes, and the false-vacuum decay rate grows exponentially with time to high accuracy.

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