Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2507.01505

Numerical treatment of annual modulation of relic neutrinos

Fabian Zimmer·Shin'ichiro Ando
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present a numerical treatment of the annual modulation of relic neutrinos due to the Sun's gravitational influence. Extending our previously developed N-1-body simulation framework from Milky Way scales to solar system dynamics, we model how cosmic neutrino background densities might vary throughout Earth's orbital cycle. We validate our numerical approach against analytical expectations from previous studies that assumed idealized relic neutrino populations. Our results suggest that the prior gravitational history of neutrinos traversing asymmetric dark matter distributions can affect annual modulation patterns. While our simulations reproduce modulation amplitudes similar to analytical predictions for heavier neutrinos, we find that the amplitude can vary considerably depending on the specific morphology of dark matter halos. These findings highlight the importance of incorporating realistic structure formation effects when predicting potential observational relic neutrino signatures.

Explore related subjects

astro-ph.COhep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Fabian Zimmer, Shin'ichiro Ando. 2025-09-19. Numerical treatment of annual modulation of relic neutrinos. https://arxiv.org/abs/2507.01505

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Angular BAO Measurements with the DESI DR1 BGS Sample

We employ a model-independent approach in both the correlation function estimation and the angular BAO feature estimation by computing the angular two-point correlation function. First, we conducted a series of tests to the available DESI tracers to check their representativeness to angular clustering; the result was that, considering the completeness of the first data release across the footprint, we could only make use of the BGS sample for the effective redshifts 0.21 (BGS1) and 0.25 (BGS2). For a reliable analysis in such low redshift, we use the bootstrap of the data itself to construct a covariance matrix that accounts for systematics. We use a purely statistical method to correct the projection effects and find that our results show reasonable agreement with the $θ_{\rm BAO}$ expected by the CPL parameters obtained by DESI DR1, being BGS1 $12.77 \pm 1.15$ degrees and BGS2 $11.70 \pm 1.21$ degrees. This means a tension at the $2.4σ$ ($2.7σ$) level for BGS1 (BGS2) CPL parametrization, while a $2.84σ$ ($3.02σ$) discrepancy within the predicted by $Λ$CDM. We conclude that, with the current sample available, the use of an angular correlation function serving as the BAO probe, although prefers the CPL parametrization, does not provide conclusive results regarding the best cosmological model.

astro-ph.CO↗
arXiv2026

Dispersion Measure Distribution of Unlocalized Fast Radio Bursts as a Probe of the Hubble Constant

We present constraints on the Hubble constant ($H_0$) derived from the observed dispersion measure (DM) distribution of unlocalized fast radio bursts (FRBs). While localized FRBs with redshift measurements have been used to investigate the Hubble tension, their sample remains limited. Here we demonstrate that unlocalized FRBs---which are far more numerous---can independently constrain $H_0$ without requiring redshift information, as cosmic expansion imprints itself on their DM distribution. Analyzing a selected sample of 2124 unlocalized FRBs from the CHIME Catalog II, we obtain $H_0 = 69^{+17}_{-15}~\mathrm{km\,s^{-1}\,Mpc^{-1}}$ at the $1σ$ confidence level, corresponding to an uncertainty of about 22\%. Disentangling the parametric degeneracy among $H_0$, the FRB spectral index $α$, and the characteristic cutoff energy $E_*$ of the FRB energy distribution would reduce the fractional uncertainty in $H_0$ to 9\%. This work constitutes the first $H_0$ measurement derived solely from the DM distribution of unlocalized FRBs, highlighting their potential as a new cosmological probe. Future joint analyses with localized FRBs promise even tighter constraints.

astro-ph.CO↗
arXiv2026

QCD Crossover Transfer Functions for Scalar-Induced Gravitational Waves in the PTA Band

Pulsar timing array (PTA) collaborations have reported evidence for a stochastic gravitational wave (GW) background in the nHz band. Should scalar-induced GWs, sourced at second order by enhanced primordial curvature perturbations, contribute to this signal, a coincidence of scales makes them directly sensitive to the softening of the equation of state around the QCD crossover. We solve the tensor and scalar equations of motion across the Standard Model (SM) thermal history and tabulate the transfer functions for direct use in present and future PTA analyses. We show that this SM effect modifies the height of the induced spectrum by up to $\approx55\%$ across the PTA band relative to the radiation-domination expectation, with either sign depending on whether the source modes cross the horizon before or after the crossover. Fitting the NANOGrav 15-year data with a broken-power-law curvature power spectrum, we find that including the crossover shifts the inferred peak amplitude and scale by an amount that could already be relevant for the comparison with primordial black hole overproduction bounds. The importance of this SM effect will grow as the statistical uncertainty on the amplitude and scale shrinks with future, more sensitive PTA datasets, at which point neglecting it could significantly bias the inference.

astro-ph.CO↗