Radiative corrections pull an isolated, long-lived massive graviton out of the gapped linear-dilaton continuum, giving a sub-MeV dark-matter candidate that can coexist with a holographic fluid component.
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Cosmological constraints on exotic injection of electromagnetic energy
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abstract
We compute cosmic microwave background (CMB) anisotropy constraints on exotic forms of energy injection in electromagnetic (e.m.) channels over a large range of timescales. These constraints are very powerful around or just after recombination, although CMB keeps some sensitivity e.g. to decaying species with lifetimes as long as $10^{25}\,$s. We review here complementary with CMB spectral distortions and primordial nucleosynthesis bounds, which dominate at earlier timescales. For the first time, we describe the effects of the e.m. energy injection on the CMB power spectra as a function of the injection epoch, using the lifetime of a decaying particle as proxy. We identify a suitable on-the-spot approximation. Our results are of interest not only for early universe relics constituting (a fraction of) the dark matter, but also for other exotic injection of e.m. radiation. For illustration, we apply our formalism to: i) Primordial black holes of mass $\in [10^{13.5},10^{16.8}]$ g, showing that the constraints are comparable to the ones obtained from gamma-ray background studies and even dominate below $\sim 10^{14}$g. ii) To a peculiar mass-mixing range in the sterile neutrino parameter space, complementary to other astrophysical and laboratory probes. iii) Finally, we provide a first estimate of the room for improvement left for forthcoming 21 cm experiments, comparing it with the reach of proposed CMB spectral distortion (PiXiE) and CMB angular power spectrum (CORE) missions. We show that the best and most realistic opportunity to look for this signal (or to improve over current constraints) in the 21 cm probe is to focus on the Cosmic Dawn epoch, $15\lesssim z\lesssim30$, where the qualitatively unambiguous signature of a spectrum in emission can be expected for models that evade all current constraints.
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representative citing papers
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Planck CMB data set upper limits on vector and axial-vector dark matter-electron couplings for masses 100 eV to 100 keV via energy injection from inelastic scattering and hydrogen absorption.
Future global 21-cm observations could beat CMB limits on TeV-scale decaying dark matter for lifetimes ≳10^15 s, especially for decays into neutrinos.
The minimal majoron framework permits simultaneous majoron dark matter and thermal leptogenesis in a constrained cosmological window set by freeze-in production, warm dark matter bounds, and indirect detection limits.
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.
Updated model-independent BBN and CMB bounds on photophilic ALPs that incorporate rare decays to light hadrons, show extended constraints for multiple reheating temperatures, and flag parameter space that may alleviate tensions in N_eff and deuterium abundance.
For ultra-light PBHs with extended mass distributions, new CMB-derived 95% exclusion bounds on f_PBH are obtained by jointly varying ΛCDM parameters, yielding f_PBH < 1.6 × 10^{-5} for a uniform distribution between 10^{15} and 10^{17} g.
The KM3NeT neutrino event may be a primordial neutrino from relic particle decay or annihilation near recombination, yielding a narrow spectral peak that evades broad power-law constraints from other telescopes.
Updated exclusion contours on lifetime, mass and abundance of decaying BSM relics from refined BBN modeling of hadronic and electromagnetic injections across multiple two-body channels.
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.
citing papers explorer
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Massive Graviton Dark Matter from a Gapped Continuum
Radiative corrections pull an isolated, long-lived massive graviton out of the gapped linear-dilaton continuum, giving a sub-MeV dark-matter candidate that can coexist with a holographic fluid component.
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Steep Redshift Evolution of the Ionizing Escape Fraction at $z = 5$--$12$: Empirical Constraints and Comparison with Simulations
Empirical three-parameter fit to f_esc(M_h,z) yields steep redshift evolution with population-averaged escape fraction rising from ~2% at z=5 to ~9% at z=12.
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Scalar-Mediated Inelastic Dark Matter as a Solution to Small-Scale Structure Anomalies
A scalar-mediated inelastic dark matter model with 100 eV splitting, Z2 symmetry forbidding elastic scattering, and a dimension-5 dipole operator reconciles dwarf galaxy observations with cosmological bounds via resonant enhancement and provides a distinct direct detection signal.
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CMB Limits on the Absorption of Light Vector and Axial-Vector Dark Matter
Planck CMB data set upper limits on vector and axial-vector dark matter-electron couplings for masses 100 eV to 100 keV via energy injection from inelastic scattering and hydrogen absorption.
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Cosmological constraints on TeV-scale dark matter subcomponents decaying between recombination and reionisation
Future global 21-cm observations could beat CMB limits on TeV-scale decaying dark matter for lifetimes ≳10^15 s, especially for decays into neutrinos.
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The Majoron Cosmological Window: Dark Matter and Thermal Leptogenesis
The minimal majoron framework permits simultaneous majoron dark matter and thermal leptogenesis in a constrained cosmological window set by freeze-in production, warm dark matter bounds, and indirect detection limits.
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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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Nucleosynthesis and CMB bounds on photophilic ALPs: a fresh look
Updated model-independent BBN and CMB bounds on photophilic ALPs that incorporate rare decays to light hadrons, show extended constraints for multiple reheating temperatures, and flag parameter space that may alleviate tensions in N_eff and deuterium abundance.
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CMB constraints on ultra-light primordial black holes with extended mass distributions
For ultra-light PBHs with extended mass distributions, new CMB-derived 95% exclusion bounds on f_PBH are obtained by jointly varying ΛCDM parameters, yielding f_PBH < 1.6 × 10^{-5} for a uniform distribution between 10^{15} and 10^{17} g.
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The KM3NeT event: a primordial high energy neutrino?
The KM3NeT neutrino event may be a primordial neutrino from relic particle decay or annihilation near recombination, yielding a narrow spectral peak that evades broad power-law constraints from other telescopes.
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Improved Big Bang Nucleosynthesis constraints on decaying massive relics
Updated exclusion contours on lifetime, mass and abundance of decaying BSM relics from refined BBN modeling of hadronic and electromagnetic injections across multiple two-body channels.
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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.