arXiv subjects

Massimo Guidi

Publications and source records attributed to Massimo Guidi.

6 recordsLinked to original sources

arXiv2026

First full-shape joint analysis of the two- and three-point correlation functions on real data: $\Lambda$CDM cosmological constraints from BOSS DR12

The three-point correlation function (3PCF) encodes cosmological information beyond the two-point correlation function (2PCF), yet a full-shape joint analysis in redshift space using real data has so far been lacking. We present the first full-shape cosmological constraints from a joint analysis of 2PCF and 3PCF in redshift space, using BOSS DR12 data, extending to real data, including Alcock--Paczy\'nski and redsfhit space distortions, the full-shape configuration-space framework validated in real space for the first time by Euclid Collaboration: Guidi et al (2026). We model both statistics adopting the velocity difference generating function (VDG) framework, incorporating non-perturbative Fingers-of-God damping, a complete Eulerian galaxy bias expansion, and infrared resummation. Fast and accurate theoretical predictions are obtained using dedicated emulators, which enable a full-shape likelihood analysis of the 3PCF and its combination with the 2PCF, varying the cosmological parameters $10^9 A_s, \omega_{\rm cdm}$ and $h$, while the baryon fraction density $\omega_{b}$ is fixed to its fiducial value. The covariance matrix is estimated from 2048 MultiDark-Patchy mocks, and an optimal data-vector compression ensures a stable covariance inversion. The perturbative model is validated against goodness-of-fit tests across different scales, and provides a good description of the joint data vector down to $r_{\rm min}^{\rm 3PCF} \sim 60\,h^{-1}{\rm Mpc}$. We find that the joint 2PCF+3PCF analysis yields significant improvements over the 2PCF-only baseline, with gains of approximately 29\%, 10\%, and 24\% on $\sigma(h)$, $\sigma(\omega_{\rm cdm})$, and $\sigma(A_s)$, respectively. The improvements mainly arise from the additional BAO cosmological information encoded in the 3PCF triangle configurations.

astro-ph.CO↗

arXiv2026

Denoising clustering covariance matrices with Rotational Invariant Estimators

Cosmological parameter inference from galaxy clustering relies critically on accurate estimates of the covariance and precision matrices. These are often obtained from a limited number of mock catalogs, introducing noise and bias in the precision matrix when the data-vector dimension becomes comparable to the number of available realizations. We present the first application of the Rotational Invariant Estimator (RIE) to the large-scale clustering of galaxies, benchmarking it against the standard sample covariance and the non-linear shrinkage estimator NERCOME for both the two-point correlation function (2PCF) and power spectrum. Using controlled synthetic data sets with analytically known covariance matrices, we estimate the covariance with all three methods across a range of mock-to-dimension ratios $q = N/D$ and data-vector sizes $D$. We then perform Bayesian inference with an EFT-based model and quantify each estimator through the Figure of Bias (FoB) and Figure of Merit (FoM). After correction for finite-$N$ effects, the sample covariance recovers unbiased average uncertainty volumes but suffers from growing best-fit scatter and bias at small $q$ due to the Dodelson--Schneider effect. Both NERCOME and RIE substantially reduce these stochastic shifts; however, the uncertainties they assign are probe-dependent. In configuration space, both estimators can yield overly tight constraints, with a bias that grows with $D$. In Fourier space, RIE delivers markedly improved best-fit stability with only mild FoM bias, whereas NERCOME tends to overestimate the constraining power. Among the estimators tested, RIE emerges as the most effective at stabilizing best-fit recovery, particularly in Fourier space, where it closely reproduces the reference posteriors even when the number of mocks barely exceeds the data-vector dimension.

astro-ph.CO↗

arXiv2026

Probing General Relativity on Cosmological Scales in the 2040s

General relativity is exquisitely tested in strong-field regimes, yet its validity on cosmological scales remains largely unexplored. Upcoming wide and deep large-scale structure surveys will access the ultra-large, linear scales where relativistic effects - Doppler terms, gravitational redshift, lensing magnification, and potential evolution - leave significant imprints in the clustering of galaxies. These signatures represent unique probes of spacetime that are inaccessible to standard Newtonian analyses but increasingly important as survey volumes grow. We outline the scientific potential of next-generation facilities, such as those envisioned within ESO's Expanding Horizons programme, to deliver the first robust measurements of relativistic effects in large-scale structure through multi-tracer power spectra and the single-tracer bispectrum of high-redshift Lyman-break galaxies. Detecting these contributions would open a new window on gravity, enabling precision tests of general relativity and its alternatives on cosmological scales in the 2040s.

astro-ph.CO↗

arXiv2026

Kinematic lensing with high-resolution spectroscopic surveys. A unique opportunity for transformative cosmology at high redshifts in the 2040s

We present a science case to perform high-redshift cosmic shear surveys for cosmology with next-generation spectroscopic instruments, such as the proposed MegaMapper and Wide-field Spectroscopic Telescope. We argue that by using the novel technique called 'kinematic lensing' (KL) it will be possible to obtain shear catalogues at redshifts between 2 and 5. We show that the signal-to-noise ratio of KL at such high redshifts is on average twice as much that expected from current weak lensing (WL) surveys such as Euclid or LSST, and several times that of the previous generation of WL surveys like DES and KiDS, even with very conservative assumptions about the fraction of spectroscopically-detected sources for which KL shear estimates will be available. This will allow cosmologists to perform joint galaxy clustering-cosmic shear analyses over unprecedented cosmic volumes and to probe the growth of structures deep in the matter-dominated era and across the onset of dark-energy domination, offering a unique opportunity to unveil the mystery of cosmic acceleration.

astro-ph.CO↗

arXiv2025

The imprints of massive neutrinos on the three-point correlation function of large-scale structures

Free-streaming of cosmic neutrinos affects the distribution and growth of cosmic structures on small scales. This enables the sum of neutrino masses $M_\nu$ to be constrained from clustering studies. We investigate the possibility of disentangling massive neutrino cosmologies with the three-point correlation function (3PCF) for the first time. We measured the isotropic connected 3PCF $\zeta$ and the reduced 3PCF $Q$ of halo catalogs from the Quijote suite of $N$-body simulations, considering $M_\nu =0.0, 0.1, 0.2,$ and $0.4 \, \mathrm{eV}$ in different redshift bins. We developed a framework to quantify the detectability of massive neutrinos for different triangle configurations and shapes, and applied it to a case compatible with a stage-IV spectroscopic survey. We also compared our results with the analysis of simulations without neutrinos, but with different $\sigma_8$ values, to test whether the 3PCF can break the well-known degeneracy between the two parameters. We found that as a result of free-streaming, the strongest signal is found for quasi-isosceles and squeezed triangles; this signal increases for decreasing redshifts. Among these configurations, elongated triangles, tracing the filamentary structure of the cosmic web, are the most affected by massive neutrinos, with a 3PCF signal increasing with $M_\nu$. A complementary source of signal comes from right-angled triangles in $Q$. Importantly, we found that the signatures of a $\sigma_8$ variation appear to be significantly different on elongated triangles in $\zeta$ and right-angled triangles in $Q$, suggesting that the 3PCF can be used to effectively break the $M_\nu - \sigma_8$ degeneracy. These results open the possibility to use the 3PCF as a powerful complementary tool for constraining neutrino masses in current and future spectroscopic surveys such as DESI, Euclid, 4MOST, and the Nancy Grace Roman Space Telescope.

astro-ph.CO↗

arXiv2024

Modeling and measuring the anisotropic halo 3-point correlation function: a coordinated study

Ongoing and future spectroscopic galaxy surveys will cover unprecedented volumes with a number of objects large enough to effectively probe clustering anisotropies through higher-order statistics. In this work, we present a novel and efficient implementation of both a model for the multipole moments of the anisotropic 3-point correlation function (3PCF) and of their estimator. To evaluate the performance of our model, we compared its predictions against direct 3PCF measurements obtained with our estimator from a set of 298 dark matter halo catalogs drawn from the $z=1$ snapshots of $N$-body simulations. For the statistical analysis, we employed a covariance matrix estimated from an independent suite of 3000 mock halo catalogs at the same redshift. We then repeated the analysis by combining the 2-point correlation function (2PCF) to the 3PCF, with and without including its anisotropic part. In the 3PCF-only analysis, the addition of the anisotropic component of the 3PCF effectively breaks the degeneracy between the growth rate $f$ and the linear bias $b_1$, significantly reducing their uncertainties. It also significantly improves the precision of the Alcock-Paczynski parameter $\varepsilon$ but does not reduce the $\sim 1$% offset we find in the estimate of the isotropic dilation parameter $\alpha$. The joint 2PCF+3PCF analysis reduces, though does not fully remove, biases in the AP and isotropic dilation parameters and breaks the $f$-$b_1$-$\sigma_8$ degeneracy, leading to tighter constraints overall. The anisotropic 3PCF adds little to the joint analysis because the tree-level 3PCF model fails to capture the anisotropic information primarily encoded on small scales and in squeezed triangle configurations. A more advanced model will be required to exploit this information fully.

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