Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.32809

Joint Angular-Power Distributions of Interfering Nanohertz Gravitational Waves

Yan-Chen Bi·Yu-Mei Wu·Qing-Guo Huang
View original source ↗Read source document ↗Export metadata ↓

Abstract

Finite populations of supermassive black-hole binaries produce fluctuations in both gravitational-wave power and pulsar timing correlations. We characterize the realization-dependent, orientation-averaged Earth-term angular correlation through its frequency-resolved Legendre coefficients. A hybrid model of bright sources and a Gaussian faint background extends the conditional Gamma distribution in the many-weak-source limit to non-central $χ^2$ statistics, yielding correlated multipoles after population marginalization. Our analytical variance decomposition and SMBHB population simulations reveal a population-dependent transition from interference dominated variance at low frequencies to population-power-dominated variance at high frequencies. In the many-weak-source regime, a multivariate lognormal approximation captures the main features of the joint distribution using only the first two log-cumulants. These results provide statistical benchmarks for fluctuations in both the overall amplitude and angular structure of the realized correlation.

Explore related subjects

astro-ph.COgr-qc

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Yan-Chen Bi, Yu-Mei Wu, Qing-Guo Huang. 2026-10-23. Joint Angular-Power Distributions of Interfering Nanohertz Gravitational Waves. https://arxiv.org/abs/2610.32809

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

KEEP EXPLORING

Related papers

arXiv2026

Cosmological Equivalence of Scalar-Tensor-Vector Modified Gravity and Cold Dark Matter

We show that Scalar-Tensor-Vector Gravity (STVG-MOG) is observationally equivalent to the standard model $Λ$CDM cosmological model for all probes that depend on isotropic and linear gravitational dynamics, including galaxy rotation curves, cluster lensing, the linear matter power spectrum P(k), $σ_8$, baryon acoustic oscillations, and the cosmic microwave background (CMB). This degeneracy arises from the scale-dependent effective gravitational coupling $G_{\mathrm{eff}}$, which ensures identical background evolution, transfer functions, and linear growth. Consequently, all early-universe, low and intermediate scale cosmological observables are equally well described by STVG-MOG without invoking non-baryonic dark matter. We argue that the equivalence implies that isotropic cosmological data alone cannot establish the physical existence of dark matter. The degeneracy is broken only by observables sensitive to large-scale, anisotropic gravitational response. In particular, recent measurements of enhanced radio-galaxy and quasar number-count dipoles at gigaparsec scales probe a regime where $G_{\mathrm{eff}}$ departs from its $Λ$CDM limit, allowing STVG-MOG to generate anisotropic bulk flows, while preserving consistency with all isotropic constraints. These observations provide a concrete pathway for empirically distinguishing modified gravity from particle dark matter.

astro-ph.CO↗
arXiv2026

Effective reheating in Gauss--Bonnet inflation with $μ(ϕ,X)$ coupling

We study effective reheating in a scalar--Gauss--Bonnet inflationary model with a phase-space-dependent coupling $μ(ϕ,X)$, in which a compact field-space feature is combined with a bounded kinetic gate. The modified inflationary background determines the pivot-scale quantities and the effective energy density at the end of inflation. These quantities are then used to derive the reheating duration $N_{\rm re}$ and temperature $T_{\rm re}$ through the thermal-history matching relation. We first perform two fixed-pivot reference scans by varying the overall Gauss--Bonnet strength $λ_{\rm GB}$ and the kinetic parameter $g_{_X}$ separately. For the reference parameter choices, increasing either parameter increases $N_{\rm re}$ and decreases $T_{\rm re}$ for the selected reheating equations of state. Additional benchmark calculations clarify how these variations depend on the dynamical regime of the model. In the $λ_{\rm GB}$ scan, the increase in $N_{\rm re}$ and the decrease in $T_{\rm re}$ persist, although both variations become strongly suppressed when the coupling is more localized or when the end of inflation is controlled more strongly by the E-model potential. In the $g_{_X}$ scan, stronger field-space localization and kinetic saturation can instead lead to a slight decrease in $N_{\rm re}$ and an increase in $T_{\rm re}$ as $g_{_X}$ is increased. When the bounded kinetic contribution is considered together with a weaker overall Gauss--Bonnet interaction, the resulting changes in the reheating quantities become nearly negligible. The fixed-pivot predictions of the representative and alternative benchmarks are compared with CMB constraints.These reheating constraints are then discussed for four representative values of the effective equation-of-state parameter, $\overline{w}_{\rm re}=-1/3,0,2/3,$ and $1$.

astro-ph.CO↗
arXiv2026

The Loud Tail of the Supermassive Black Hole Binary Population: Multimessenger Candidates and Prospects for SKAO

We assess whether electromagnetically identified supermassive black hole (SMBH) binary candidates populate the rare, high-amplitude tail of the gravitational wave (GW) amplitude distribution. Using an SMBH binary population model fitted to the NANOGrav 15-year data, we find that 3C~66B and Mrk~501 are likely to stand out from the GW background, making them promising targets for individual-source searches. Furthermore, we show that individual detections can probe the binary hardening mechanism, as models with strong environmental hardening predict a higher abundance of individually resolvable binaries than purely GW-driven models. Applying the same population fits and accounting for the confusion noise from the unresolved population, we forecast that the Square Kilometre Array Observatory (SKAO) will resolve tens of individual binaries, with 3C~66B robustly detectable.

astro-ph.CO↗