Accounting for the minimal mass spread of primordial black holes from gravitational collapse suppresses the Poltergeist GW background to the level of generic scalar-induced signals and reopens ultra-light PBH parameter space.
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Relic neutrino decoupling with flavour oscillations revisited
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abstract
We study the decoupling process of neutrinos in the early universe in the presence of three-flavour oscillations. The evolution of the neutrino spectra is found by solving the corresponding momentum-dependent kinetic equations for the neutrino density matrix, including for the first time the proper collision integrals for both diagonal and off-diagonal elements. This improved calculation modifies the evolution of the off-diagonal elements of the neutrino density matrix and changes the deviation from equilibrium of the frozen neutrino spectra. However, it does not vary the contribution of neutrinos to the cosmological energy density in the form of radiation, usually expressed in terms of the effective number of neutrinos, N_eff. We find a value of N_eff=3.045, in agreement with previous theoretical calculations and consistent with the latest analysis of Planck data. This result does not depend on the ordering of neutrino masses. We also consider the effect of non-standard neutrino-electron interactions (NSI), predicted in many theoretical models where neutrinos acquire mass. For two sets of NSI parameters allowed by present data, we find that N_eff can be reduced down to 3.040 or enhanced up to 3.059.
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Conventional BBN fitting for negative Delta N_eff is unphysical; a consistent treatment via entropy dilution after neutrino decoupling yields significantly different bounds.
DESI DR1 full-shape clustering yields Ω_m = 0.2962 ± 0.0095 and σ_8 = 0.842 ± 0.034 in flat ΛCDM, tightening to H_0 = 68.40 ± 0.27 km/s/Mpc with CMB and DESY3, while favoring w_0 > -1, w_a < 0 and limiting neutrino mass sum to < 0.071 eV.
Supernova models yield coupling limits g_a ≲ 0.9×10^{-10} and g_φ ≲ 0.4×10^{-10} for masses above 100 keV from gamma-ray observations, plus stronger trapping-regime limits from explosion energy, that are difficult to reconcile with a muon g-2 explanation.
Dynamical Tsallis q during WIMP freeze-out leaves residual nonextensivity that alters neutrino energy density and N_eff through a phenomenological memory channel while staying within observational limits.
Lepton parity stabilizes a Majorana fermion as freeze-in dark matter produced via right-handed neutrino or Higgs decays, yielding detectable gravitational waves or ΔN_eff depending on scalar couplings.
Final Planck CMB data confirms the flat 6-parameter ΛCDM model with Ω_c h² = 0.120 ± 0.001, Ω_b h² = 0.0224 ± 0.0001, n_s = 0.965 ± 0.004, τ = 0.054 ± 0.007, H_0 = 67.4 ± 0.5 km/s/Mpc, and no strong evidence for extensions.
A 22 MeV Dirac dark matter particle in a U(1)_{Lμ-Lτ} model annihilates to muon and tau neutrinos that oscillate to explain the SK excess while matching thermal relic abundance.
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.
CMB data limits the s-wave annihilation cross section of thermal dark matter particles to ≲ 10^{-30} cm³/s scaled by PBH fraction and mass for PBHs heavier than ~10^{-10} solar masses.
Presents the science case, reference design, and project plan for the CMB-S4 ground-based CMB experiment.
A mini-review of axion phenomenology showing how light bosons can account for dark matter, drive cosmic acceleration, or contribute to relativistic backgrounds in the early and late Universe.
A review summarizing the Hubble constant tension and proposed solutions from new physics that restore agreement between Planck CMB data and local H0 measurements within 1-2 sigma.
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DESI 2024 VII: Cosmological Constraints from the Full-Shape Modeling of Clustering Measurements
DESI DR1 full-shape clustering yields Ω_m = 0.2962 ± 0.0095 and σ_8 = 0.842 ± 0.034 in flat ΛCDM, tightening to H_0 = 68.40 ± 0.27 km/s/Mpc with CMB and DESY3, while favoring w_0 > -1, w_a < 0 and limiting neutrino mass sum to < 0.071 eV.