Heterotic string theory implies the QCD axion mass is bounded below by 0.5 neV and typically falls in [0.5, 0.8] neV across most compactifications.
Glimmers from the axiverse,
13 Pith papers cite this work. Polarity classification is still indexing.
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O(100–10^5) light string axions enhance PBH spin-up during Hawking evaporation, boosting superradiant dark-matter cloud efficiency and expanding the micro-boson-star parameter space while contributing negligibly to ΔN_eff.
In F-theory GUTs, non-universal ALPs induced by hypercharge flux satisfy g_aγ/m_a well below the QCD axion prediction when gauge couplings unify near the string scale.
Proposes searching for GeV-scale ALPs in ultra-peripheral collisions at RHIC via γγ → a → γγ, estimating sensitivity to m_a ~2-5 GeV and g_aγγ ≳4e-4 GeV^{-1} with existing PHENIX data.
Multi-axion solutions to the strong CP problem produce varied mass-coupling patterns set by PQ symmetry breaking structure and QCD-EM anomaly alignment, summarized by a general sum rule for N-axion systems.
Hierarchical Bayesian analysis of GWTC-5 binary black hole spins finds no evidence for superradiant axions and excludes masses 1.7e-14 to 3.3e-12 eV at 95% CL.
The bound Λ_QG ≲ 2π √S f holds for C2 and C4 axions in Type IIB Calabi-Yau compactifications even near Kähler moduli space boundaries where co-scaling fails.
Projections for IAXO in two-axion parameter space plus spectral analysis of flavor oscillations show where the experiment can discriminate multi-axion signals from single-axion ones, extending to N-axion cases.
A light axion spectator induces post-inflation tachyonic phases that produce a nearly scale-invariant boost to the curvature power spectrum and alter key inflationary observables in a largely potential-independent manner.
New upper limits on ultralight axion dark matter fraction (<1.5% at 10^{-26} eV, <9% at 10^{-25} eV at 95% CL) from combined CMB lensing data, plus marginal 2.1σ preference at 10^{-24.5} eV driven by few points.
Turbulent magnetic fields enhance axion-photon conversion signals from supernovae, improving limits on axion-proton and axion-photon couplings by up to two orders of magnitude.
QCD axions constrain F-theory base threefolds to have rigid or flux-rigidified divisors, yielding typical axion masses around 10^{-9} eV and decay constants near 10^{15} GeV in allowed regions.
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.
citing papers explorer
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Heterotic String Theory Suggests a QCD Axion Near 0.5 neV
Heterotic string theory implies the QCD axion mass is bounded below by 0.5 neV and typically falls in [0.5, 0.8] neV across most compactifications.
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String Axiverse Enhancement of Superradiant Dark Matter Production
O(100–10^5) light string axions enhance PBH spin-up during Hawking evaporation, boosting superradiant dark-matter cloud efficiency and expanding the micro-boson-star parameter space while contributing negligibly to ΔN_eff.
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Testing F-theory GUTs with the Axiverse
In F-theory GUTs, non-universal ALPs induced by hypercharge flux satisfy g_aγ/m_a well below the QCD axion prediction when gauge couplings unify near the string scale.
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Searches for GeV-Scale ALPs at RHIC
Proposes searching for GeV-scale ALPs in ultra-peripheral collisions at RHIC via γγ → a → γγ, estimating sensitivity to m_a ~2-5 GeV and g_aγγ ≳4e-4 GeV^{-1} with existing PHENIX data.
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The structure of multi-axion solutions to the strong CP problem
Multi-axion solutions to the strong CP problem produce varied mass-coupling patterns set by PQ symmetry breaking structure and QCD-EM anomaly alignment, summarized by a general sum rule for N-axion systems.
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No Evidence for Superradiant Axions in LIGO-Virgo-KAGRA GWTC-5 Binary Black Hole Spins
Hierarchical Bayesian analysis of GWTC-5 binary black hole spins finds no evidence for superradiant axions and excludes masses 1.7e-14 to 3.3e-12 eV at 95% CL.
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Quantum Gravity Cutoff from Axions: A Type IIB Landscape Study
The bound Λ_QG ≲ 2π √S f holds for C2 and C4 axions in Type IIB Calabi-Yau compactifications even near Kähler moduli space boundaries where co-scaling fails.
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Counting axions with IAXO
Projections for IAXO in two-axion parameter space plus spectral analysis of flavor oscillations show where the experiment can discriminate multi-axion signals from single-axion ones, extending to N-axion cases.
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Tachyonic Encore: A universal shift of inflationary observables
A light axion spectator induces post-inflation tachyonic phases that produce a nearly scale-invariant boost to the curvature power spectrum and alter key inflationary observables in a largely potential-independent manner.
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The Atacama Cosmology Telescope: Probing new signatures of ultralight axions with gravitational lensing
New upper limits on ultralight axion dark matter fraction (<1.5% at 10^{-26} eV, <9% at 10^{-25} eV at 95% CL) from combined CMB lensing data, plus marginal 2.1σ preference at 10^{-24.5} eV driven by few points.
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Magnetic Turbulence Boosts Supernova Signals of Axion-Photon Conversion
Turbulent magnetic fields enhance axion-photon conversion signals from supernovae, improving limits on axion-proton and axion-photon couplings by up to two orders of magnitude.
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Constraining F-theory Model Building with QCD Axions
QCD axions constrain F-theory base threefolds to have rigid or flux-rigidified divisors, yielding typical axion masses around 10^{-9} eV and decay constants near 10^{15} GeV in allowed regions.
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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.