arXiv subjects

Simone Sartori

Publications and source records attributed to Simone Sartori.

4 recordsLinked to original sources

arXiv2026

CMB lensing imprints of cosmic voids in DESI Legacy Survey DR9 LRGs with photometric redshift calibration

The lensing imprint of cosmic voids in the Cosmic Microwave Background (CMB) provides a powerful test of the $Λ$CDM model. However, recent studies report a "lensing-is-low" tension between observations and mock predictions. To investigate this, we measure the stacked CMB lensing signal of 3D cosmic voids identified in the DESI Legacy Survey DR9 Luminous Red Galaxy (LRG) sample, cross-correlated with the Planck 2018 lensing map. We compare our observations to $Λ$CDM templates derived from Buzzard mocks, critically calibrated using over one million DESI spectra to perfectly match the sparseness and photometric redshift error distributions of the observed data. By categorizing voids based on their gravitational potential, we disentangle the signals of void-in-voids and void-in-clouds, achieving two independent record detection significances of $\sim 17σ$. We find full agreement between observations and simulated $Λ$CDM templates across all void populations and redshift bins ($0.35\! <\! z\! <\! 0.95$), measuring an amplitude parameter $A_κ= 1.016 \pm 0.054$ for the full sample. This highlights the necessity of accurate systematic control, effectively resolving the reported lensing tension within this dataset. This proceeding summarizes the results presented in Sartori et al. (2025).

astro-ph.CO↗

arXiv2026

The Back-in-time Void Finder: dynamical identification of cosmic voids through optimal transport reconstruction

Cosmic voids have increasingly emerged as a powerful cosmological probe. However, their large spatial extent and intrinsically underdense environments make their identification highly sensitive to shot noise, redshift-space distortions (RSD), and observational systematics, particularly for topological and density-based void definitions. We introduce the Back-In-Time Void Finder (BitVF), a novel dynamical and physically motivated algorithm that identifies cosmic voids as regions of negative divergence of the Lagrangian displacement field reconstructed from the present-day tracer distribution. The reconstruction relies on an optimized discrete optimal transport algorithm that recovers the backward-in-time dynamics of tracers, naturally accounting for tracer bias without relying on cosmological assumptions. We validate BitVF against the widely used topological void finder REVOLVER using high-resolution N-body simulations, showing that it produces void catalogs with smoother and more physically motivated density profiles, as well as abundances that are more stable under tracer subsampling and shot noise. We further apply it to realistic DESI-like mock light-cone galaxy catalogs, demonstrating that it intrinsically mitigates redshift-space systematic effects, preserving real-space void size functions more faithfully than topological methods. Modeling RSD, the reconstruction can be combined with a fiducial cosmology and an assumed tracer bias within a bias-corrected Kaiser framework, yielding reconstructed-space void catalogs consistent with real-space statistics across redshift. Its performance is characterized as a function of the main internal parameters, showing an optimal balance between accuracy, computational efficiency, and applicability to stage IV galaxy surveys. BitVF will be publicly released within the CosmoBolognaLib.

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↗