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arxiv: 2606.24868 · v1 · pith:SFW2JBKNnew · submitted 2026-06-23 · 🌌 astro-ph.CO

Exploring Gravitational Wave Signatures Due to Primordial Non-gaussianity and Large Scale Structure Using SKAO

H. V. Ragavendra , Giulia Capurri , Alina Mierna , Gabriele Perna , Federico Semenzato , Nicola Bartolo , Daniele Bertacca , Lorenzo Valbusa Dall'Armi
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Sabino Matarrese Matteo Pegorin Angelo Ricciardone
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classification 🌌 astro-ph.CO
keywords stochastic gravitational wavesprimordial non-Gaussianityparity violationlarge-scale structureSKAOscalar-induced gravitational waveschirality
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The pith

Cross-correlating the gravitational wave background with large-scale structure tracers enhances signal detection for SKAO observations.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper examines strategies for using the stochastic gravitational wave background detectable by the Square Kilometre Array Observatory to study precision cosmology. It focuses on scalar-induced gravitational waves that are sensitive to primordial non-Gaussianity at small scales and to parity violation through imprinted chirality. The analysis shows that auto-correlation of the wave signal is hindered by astrophysical shot noise. Cross-correlating the signal with independent large-scale structure tracers improves the signal-to-noise ratio and helps separate astrophysical from cosmological contributions. The enhanced capabilities of SKAO enable these measurements.

Core claim

Scalar-induced gravitational waves carry unique features sensitive to primordial non-Gaussianity on small scales and can exhibit scale-dependent helicity from a parity-odd primordial trispectrum. The standard angular auto-correlation analysis of the stochastic gravitational wave background is limited by astrophysical shot noise. Cross-correlating the gravitational wave signal with large-scale structure tracers enhances the signal-to-noise ratio and isolates the astrophysical and cosmological components in the background.

What carries the argument

Cross-correlation between the stochastic gravitational wave background and large-scale structure tracers to mitigate shot noise and isolate components.

Load-bearing premise

Astrophysical shot noise dominates standard auto-correlation analyses of the gravitational wave background, and cross-correlations introduce no comparable new systematics.

What would settle it

A measurement showing whether the cross-correlation power spectrum with LSS tracers yields a significantly higher signal-to-noise ratio than the auto-correlation spectrum alone.

Figures

Figures reproduced from arXiv: 2606.24868 by Alina Mierna, Angelo Ricciardone, Daniele Bertacca, Federico Semenzato, Gabriele Perna, Giulia Capurri, H. V. Ragavendra, Lorenzo Valbusa Dall'Armi, Matteo Pegorin, Nicola Bartolo, Sabino Matarrese.

Figure 1
Figure 1. Figure 1: Plot of the spectral energy density ℎ 2ΩGW for SIGWs in the Gaussian case (red solid line) as well as accounting for the presence of non-Gaussianity (blue, orange, green solid lines) in the case of a log-normal scalar power spectrum seed [adapted from Perna et al. (2024)]. distinctive signature of a GW signal, it does not reveal its origin. The measured correlation, in general, is the result of a superposi… view at source ↗
Figure 2
Figure 2. Figure 2: We illustrate the spectral densities ΩGW and Ω𝑉 GW of SIGW, while accounting for T given by Eq. (8). The scalar power spectrum PS (𝑘) in this case is described by a lognormal peak [Eq. (11)]. We present ΩGW and Ω𝑉 GW in red and blue curves respectively, and indicate negatives values of Ω𝑉 GW in green. We present the corresponding degree of chirality Π𝑘 in the panel below. We have set 𝐴p = 10−2 , 𝑔NL = 𝑔˜NL… view at source ↗
read the original abstract

This chapter explores theoretical and observational strategies to use the stochastic gravitational-wave background detectable by Square Kilometre Array Observatory (SKAO) as a probe of precision cosmology. We detail the critical phenomenon of scalar-induced gravitational waves, demonstrating their unique features and their sensitivity to primordial non-Gaussianity on scales much smaller than those probed by the cosmic microwave background and large-scale structure. We investigate the phenomenology of parity violation in the early Universe through the chirality imprinted in the stochastic gravitational-wave background, demonstrating that a parity-odd primordial trispectrum can generate a detectable scale-dependent helicity. On the observational side, we point out that the standard gravitational-wave angular auto-correlation analysis is significantly limited by astrophysical shot noise. We show that cross-correlating the gravitational wave signal with independent large-scale structure tracers enhances the signal-to-noise ratio and allows us to isolate the astrophysical and cosmological components in the background. These results can be achieved only thanks to the enhanced sensitivity of SKAO, extensive sky coverage, and high angular resolution, which together make such targets observationally feasible.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 0 minor

Summary. The manuscript explores theoretical and observational strategies to use the stochastic gravitational-wave background (SGWB) detectable by SKAO as a probe of precision cosmology. It discusses scalar-induced GWs and their sensitivity to primordial non-Gaussianity on small scales, parity violation via chirality from a parity-odd primordial trispectrum, and proposes that cross-correlating the GW signal with independent LSS tracers enhances SNR while isolating astrophysical and cosmological components, enabled by SKAO's sensitivity, sky coverage, and angular resolution.

Significance. If the unshown calculations, error budgets, and quantitative forecasts hold, the work could provide new handles on small-scale primordial physics and component separation in SGWB analyses. The cross-correlation strategy addresses a known limitation of auto-correlation analyses, but its significance depends on validation that LSS tracers do not reintroduce comparable contamination.

major comments (1)
  1. [Abstract (final paragraph)] Abstract (final paragraph): the claim that cross-correlating with LSS tracers 'enhances the signal-to-noise ratio and allows us to isolate the astrophysical and cosmological components' rests on the assumption that these tracers introduce no systematics or selection biases comparable to astrophysical shot noise. No error budget or covariance analysis is referenced to support this isolation, making the central observational claim load-bearing but unsupported in the presented text.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful and constructive review of our manuscript. The comment on the abstract is well taken, and we address it directly below. We will revise the manuscript to strengthen the presentation of the supporting analysis.

read point-by-point responses

  1. Referee: [Abstract (final paragraph)] Abstract (final paragraph): the claim that cross-correlating with LSS tracers 'enhances the signal-to-noise ratio and allows us to isolate the astrophysical and cosmological components' rests on the assumption that these tracers introduce no systematics or selection biases comparable to astrophysical shot noise. No error budget or covariance analysis is referenced to support this isolation, making the central observational claim load-bearing but unsupported in the presented text.

    Authors: We agree that the abstract statement would be stronger with explicit pointers to the supporting calculations. The full manuscript derives the cross-correlation SNR, presents the relevant covariance matrices, and discusses mitigation of LSS tracer systematics (including selection biases and shot noise) in Sections 3.2 and 4. To address the referee's concern, we will revise the abstract to reference these sections and add a concise statement on the error budget. We will also expand the main text to more explicitly compare residual LSS systematics against astrophysical shot noise. These changes will be incorporated in the revised version. revision: yes

Circularity Check

0 steps flagged

No significant circularity; claims rest on external literature and SKAO observational properties without self-referential reductions.

full rationale

The provided abstract and text outline strategies for scalar-induced GWs sensitive to primordial non-Gaussianity, parity violation via chirality, and cross-correlation with LSS tracers to mitigate shot noise. No equations, fitted parameters, or predictions are exhibited that reduce by construction to inputs. No self-citations are invoked as load-bearing uniqueness theorems or ansatze. The central claim about SNR enhancement via cross-correlation is presented as a consequence of SKAO sensitivity and coverage, independent of any internal definitions or prior author results within the paper itself. This is the standard case of a self-contained proposal against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only; no explicit free parameters, axioms, or invented entities are stated.

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