arXiv subjects

Francesco Sorrenti

Publications and source records attributed to Francesco Sorrenti.

7 recordsLinked to original sources

arXiv2026

Nonlinear velocity power spectrum: modeling the cosmological dependence on the Hubble constant and cold dark matter density

In this paper we present a semi-analytical model for the velocity power spectrum in $\La$CDM cosmology for wave numbers $k<1/$Mpc. We mainly concentrate on the dominant divergence part but also present some results on the vorticity contribution. We divide cosmological parameters into evolution and shape parameters and model the dependence of the evolution parameter $h$ and of the shape parameter $\om_{\rm cdm}$ with an accuracy better than 2.5\%. A surprising finding of our study is that the velocity power spectrum becomes independent of $\om_{\rm cdm}$ on nonlinear scales. A python implementation of the model is publicly available.

astro-ph.CO↗

arXiv2026

Reconstructing the kinematics of Laniakea using Type Ia Supernovae

We develop a kinematic framework that relates the monopole, dipole, and quadrupole of the luminosity distance to an ellipsoidal peculiar velocity field describing the dynamics of the Laniakea supercluster. By properly accounting for the transformations between the CMB and Laniakea reference frames and selecting Type Ia supernovae within the volume associated with the superstructure, we show that luminosity distance multipoles encode the expansion and shear of the local velocity field. This allows the ellipsoidal kinematics of Laniakea to be inferred directly from supernova observations. Our results provide a physically motivated interpretation of luminosity distance anisotropies within the volume dynamically dominated by Laniakea as signatures of its large-scale kinematics. The framework developed here suggests that future supernova observations can enable the independent reconstruction of large-scale structures in the local Universe

astro-ph.CO↗

arXiv2025

Anchors no more: Using peculiar velocities to constrain $H_0$ and the primordial Universe without calibrators

We develop a novel approach to constrain the Hubble parameter $H_0$ and the primordial power spectrum amplitude $A_\mathrm{s}$ using type Ia supernovae (SNIa) data. By considering SNIa as tracers of the peculiar velocity field, we can model their distance and their covariance as a function of cosmological parameters without the need of calibrators like Cepheids; this yields a new independent probe of the large-scale structure based on SNIa data without distance anchors. Crucially, we implement a differentiable pipeline in JAX, including efficient emulators and affine sampling, reducing inference time from years to hours on a single GPU. We first validate our method on mock datasets, demonstrating that we can constrain $H_0$ and $\log 10^{10}A_\mathrm{s}$ within $10\%$ and $15\%$, respectively, using $\mathcal{O}(10^3)$ SNIa. We then test our pipeline with SNIa from an $N$-body simulation, obtaining $6\%$-level unbiased constraints on $H_0$ with a moderate noise level. We finally apply our method to Pantheon+ data, constraining $H_0$ at the $15\%$ level without Cepheids when fixing $A_\mathrm{s}$ to its $\it{Planck}$ value. On the other hand, we obtain $20\%$-level constraints on $\log 10^{10}A_\mathrm{s}$ in agreement with $\it{Planck}$ when including Cepheids in the analysis. In light of upcoming observations of low redshift SNIa from the Zwicky Transient Facility and the Vera Rubin Legacy Survey of Space and Time, surveys for which our method will develop its full potential, we make our code publicly available.

astro-ph.CO↗

arXiv2025

Exploring the cosmic microwave background dipole direction using gamma-ray bursts

We search for dipole variations in the Hubble constant $H_0$ using gamma-ray burst (GRB) data, as such anisotropies may shed light on the Hubble tension. We employ the most recent and reliable GRB catalogs from the $E_{p}-E_{iso}$ and the $L_0-E_{p}-T$ correlations. Despite their large uncertainties, GRBs are particularly suited for this analysis due to their redshift coverage up to $z\sim9$, their isotropic sky distribution that minimizes directional bias, and their strong correlations whose normalizations act as proxies for $H_0$. To this aim, a whole sky scan - partitioning GRB data into hemispheres - enabled to define dipole directions by fitting the relevant GRB correlation and cosmological parameters. The statistical significance across the full $H_0$ dipole maps, one per correlation, is then evaluated through the normalization differences between hemispheres and compared against the CMB dipole direction. The method is then validated by simulating directional anisotropies via Markov Chain Monte Carlo analyses for both correlations. Comparison with previous literature confirms the robustness of the method, while no significant dipole evidence is detected, consistently with the expected isotropy of GRBs. This null result is discussed in light of future analyses involving larger datasets.

astro-ph.CO↗

arXiv2025

The low multipoles in the Pantheon+SH0ES data

In previous work we have shown that the dipole in the low redshift supernovae of the Pantheon+SH0ES data does not agree with the one inferred from the velocity of the solar system as obtained from CMB data. We interpreted this as the presence of significant bulk velocities. In this paper we study the monopole, dipole and quadrupole in the Pantheon+SH0ES data. We find that in addition to the dipole also both, the monopole and the quadrupole are detected with high significance. They are of similar amplitudes as the bulk flow. While the monopole is only significant at very low redshift, the quadrupole even increases with redshift.

astro-ph.CO↗

arXiv2024

A local infall from a cosmographic analysis of Pantheon+

We present a model independent analysis of the Pantheon+ supernova sample and study the dependence of the recovered values of $H_0$, $q_0$ and $j_0$ on the redshift cut and on the modeling of peculiar velocities. In addition to the bulk velocity discussed previously, we also find a significant infall that we attribute to the presence of an overdensity out to a radius of $R\simeq 120h^{-1}$Mpc.

astro-ph.CO↗

arXiv2023

The Dipole of the Pantheon+SH0ES Data

In this paper we determine the dipole in the distance redshift relation from the Pantheon+ data. We find that, while its amplitude roughly agrees with the dipole found in the cosmic microwave background which is attributed to the motion of the solar system with respect to the cosmic rest frame, the direction is different with a significance of slightly more than $3\si$. While the amplitude depends on the lower redshift cutoff, the direction is quite stable. For redshift cuts of order $z_{\rm cut} \simeq 0.05$ and higher, the dipole is no longer detected with high statistical significance. An important rôle seems to be played by the redshift corrections for peculiar velocities.

astro-ph.CO↗