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The Irreducible Axion Background

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arxiv 2209.06216 v2 pith:WV366DXE submitted 2022-09-13 hep-ph astro-ph.COastro-ph.HE

classification hep-phastro-ph.COastro-ph.HE
keywords axionaxionsmagnitudeordersalmostconstraintdensitygamma
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

Searches for dark matter decaying into photons constrain its lifetime to be many orders of magnitude larger than the age of the Universe. A corollary statement is that the abundance of any particle that can decay into photons over cosmological timescales is constrained to be much smaller than the cold dark-matter density. We show that an $\textit{irreducible}$ freeze-in contribution to the relic density of axions is in violation of that statement in a large portion of the parameter space. This allows us to set stringent constraints on axions in the mass range $100\rm \;eV - 100\; MeV$. At $10\rm \; keV$ our constraint on a photophilic axion is $g_{a\gamma \gamma} \lesssim 8.1 \times 10^{-14}~{\rm GeV}^{-1}$, almost three orders of magnitude stronger than the bounds established using horizontal branch stars; at $100~{\rm keV}$ our constraint on a photophobic axion coupled to electrons is $g_{aee} \lesssim 8.0 \times 10^{-15}$, almost four orders of magnitude stronger than present results. Although we focus on axions, our argument is more general and can be extended to, for instance, sterile neutrinos.

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Forward citations

Cited by 9 Pith papers

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

  1. The Dark Dimension meets the Axiverse

    hep-ph 2026-07 conditional novelty 7.0 of 10

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  3. Heavy neutral leptons from light scalar in fixed target and forward search experiments

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  4. Beyond thermal approximations: Precise cosmological bounds on Axion-Like Particles

    astro-ph.CO 2026-02 conditional novelty 6.0 of 10

    Solving the momentum-dependent Boltzmann equation and propagating the exact non-thermal ALP spectrum into CMB analyses yields 95% limits f_a>1.63e6 GeV (e), 9.41e6 GeV (mu), 8.06e4 GeV (tau), and g_a_gamma<1.98e-8 GeV^-1.

  5. Loop-Level Lepton Flavor Violation and Diphoton Signals in the Minimal Left-Right Symmetric Model

    hep-ph 2025-12 conditional novelty 6.0 of 10

    Recasting axion limits onto the one-loop H3 couplings of the minimal left-right symmetric model excludes the right-handed scale up to 2×10^9 GeV and could eventually probe 6×10^11 GeV.

  6. Improved cosmological constraints on axion-lepton interactions

    hep-ph 2025-11 conditional novelty 6.0 of 10

    For axion masses above 0.1 eV, cosmology provides the strongest known limits on axion couplings to muons, taus, and flavor-violating tau channels, excluding decay constants up to 10^8 GeV.

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    hep-ph 2025-07 conditional novelty 6.0 of 10

    Roughly 10 to 15 percent of explicit string theory axiverse models are disfavored by CMB reionization data unless reheating stayed below about 10^10 GeV.

  8. Probing the Cosmic Axion Background via Axion-Photon Conversion in Filaments

    hep-ph 2026-07 conditional novelty 5.0 of 10

    Axion-photon conversion in cosmic filaments would turn dark-matter decay into a gamma-ray background, and the calculated flux excludes axion masses below ~10^-5 eV for GeV–TeV dark matter with lifetimes below ~10^30 s.

  9. Neutrino lines and photon continua from cascade dark matter decay

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