arXiv subjects

Isaac Tutusaus

Publications and source records attributed to Isaac Tutusaus.

At least 19 recordsLinked to original sources

arXiv2026

Growth, geometry, and early-universe split of the matter density parameter $\Omega_{\rm m}$

While the $\Lambda$ cold dark matter ($\Lambda$CDM) model can successfully reproduce the measurements of many cosmological probes, some discrepancies have recently emerged. Therefore, it is necessary to test the standard cosmological model for consistency. An important stress test is to separate the influence of different cosmological regimes on the parameter inference. We treat three regimes separately here: geometry, growth, and the early universe. The geometrical regime concerns the expansion and curvature history, while the growth regime governs structure formation and the early-universe regime affects physics prior to recombination. Previous analyses have performed the split between geometry and growth, whereas we also consider the early universe influence separately. We perform this split for the present day matter density parameter $\Omega_{\rm m}$ using multiple cosmological observables. The used data are galaxy clustering and weak lensing statistics (3x2pt) from the Dark Energy Survey (DES), cosmic microwave background (CMB) data from Planck, spectroscopic baryon acoustic oscillations (BAO) from the Dark Energy Spectroscopic Instrument (DESI), type-Ia supernovae (SNe Ia) samples from Pantheon+, and redshift-space distortions (RSD) from a collection of galaxy surveys. For each of these probes, we introduce a phenomenological split into these three regimes. This work shows a strong correlation between the geometric and the early regime for the matter density, but no strong correlation between the growth regime and the others. All regimes are compatible in the posterior distribution, however the difference between the geometry and the early regimes, $\Delta\Omega_{\rm m}^{\rm geo,early}$, is 2$\sigma$ apart from 0.

astro-ph.CO↗

arXiv2026

cloelib: A Flexible Python Library for Computing Cosmological Observables in the Euclid Era

cloelib is a Python library developed to compute cosmological observables within the Cosmology Likelihood for Observables in Euclid (CLOE) ecosystem (cloe-org). As cosmology enters a precision era driven by galaxy survey missions such as Euclid, there is a growing need for flexible, efficient, and differentiable software capable of supporting next-generation inference pipelines. cloelib addresses these demands through a modular architecture that interfaces seamlessly with established Boltzmann solvers whilst incorporating JAX-based automatic differentiation to enable gradient-based methods. The library defines consistent protocols for background evolution, perturbations, and non-linear structure formation, and supports a wide range of observables, including photometric and spectroscopic large-scale structure probes, as well as cross-correlations with the Cosmic Microwave Background and galaxy clusters. In its finalised form, cloelib is intended to serve as the reference theory computation infrastructure for Euclid's first cosmological release, bridging traditional numerical cosmology with modern optimisation techniques and emerging machine learning approaches to inference.

astro-ph.CO↗

arXiv2026

cloelike: A Python Library for Cosmological Likelihood Inference in the Euclid Era

cloelike is a Python package providing modular, composable Gaussian likelihood classes for the main cosmological large-scale structure observables targeted by the ESA Euclid space mission. It is a core component of the CLOE (Cosmology Likelihood for Observables in Euclid) ecosystem and interfaces directly with cloelib for theoretical predictions and euclidlib for reading official Euclid data products. The package implements Gaussian likelihoods covering harmonic angular power spectra and real-space two-point correlation functions for weak lensing (WL), photometric galaxy clustering (GCph), and Galaxy-Galaxy Lensing (GGL) in all joint probe combinations (3x2pt, 2x2pt), as well as spectroscopic full-shape power spectrum multipoles, and baryonic Acoustic oscillations (BAO). cloelike is actively used in internal Euclid Consortium analyses and is openly released to support community validation and reproducibility.

astro-ph.CO↗

arXiv2026

The impact of evolving dark energy on the Weyl potential measured from the Dark Energy Survey Year 3 data

Measurements from the Dark Energy Survey (DES) Year 3 data have shown that the Weyl potential -- the sum of the spatial and temporal distortions of the geometry -- evolves more slowly than predicted by General Relativity, assuming a $\Lambda$CDM background evolution. An evolving dark energy with a phantom crossing, as preferred by the Dark Energy Spectroscopic Instrument (DESI), is expected to decrease the depth of the gravitational potentials through a stronger acceleration than in $\Lambda$CDM, potentially solving the tension with General Relativity. In this paper, we show that $w_0w_a$CDM models indeed reduce the tension with respect to $\Lambda$CDM, down to a level of $1.6-2.2\sigma$, depending on the treatment of CMB lensing. This reduction is not due to an increase in the Weyl potential's uncertainties, but truly to the impact of the evolving background on the theoretical predictions in General Relativity. More data are needed to robustly determine if evolving dark energy fully explains the low value of the Weyl potential at intermediate redshifts, or if modifications of gravity or interactions in the dark sector are needed, which could simultaneously stabilize the phantom crossing indicated by DESI.

astro-ph.CO↗

arXiv2026

Brightest Cluster Galaxy ellipticity as proxy for halo shape: Orientation bias, assembly bias, and potential selection effects in SZ-selected clusters

The orientation of triaxial galaxy clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (e.g., richness and weak-lensing signal) of galaxy clusters. In this work, we use the observed shape of the central Brightest Cluster Galaxy (BCG) as proxy for the orientation along the line-of-sight for clusters selected via the Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) surveys, matched to optically selected clusters from the Dark Energy Survey Year 3 (DES). We construct two samples of clusters that are designed to be identical in SZ mass estimate and redshift but with the roundest vs. the most elliptical BCGs, which we expect to correspond to BCGs (and clusters) with major axes aligned along the line-of-sight vs. in the plane of the sky, respectively. We find that the optical richness of round-BCG clusters is $\sim 10$\% larger than that of elliptical-BCG clusters, in agreement with the expectation from projection effects and presenting the first such detection in data. The density profiles, however, are not in agreement with the expectation from projection effects: the 1-halo term (below $6~h^{-1}\rm{Mpc}$) of both the weak-lensing and galaxy density profiles are the same for the subsamples, contrary to previous studies based on X-ray selected clusters. In the 2-halo regime (above $6~h^{-1}\rm{Mpc}$), we find a significant excess of the elliptical-BCG cluster profiles compared to the round-BCG cluster profiles, which is the opposite of the expectation from numerical simulations. We hypothesize that the intrinsic shape of the BCG reflects not just the orientation angle, but also intrinsic properties of the cluster which can affect both the SZ signal and the amplitude of the 2-halo term.

astro-ph.CO↗

arXiv2025

Testing modified gravity with 3x2pt analyses in galaxy mocks

Stage-IV surveys will enable unprecedented tests of gravity on cosmological scales. However, assuming General Relativity in the analysis of large-scale structure could introduce systematic biases if gravity deviates from GR at these scales. Modified gravity theories, such as the Hu-Sawicki formulation of $f(R)$ gravity, offer an alternative explanation for cosmic acceleration without invoking a cosmological constant, while remaining consistent with Solar System tests through screening mechanisms. In this work, we quantify the cosmological parameter biases that arise when using a combination of galaxy clustering and weak-lensing data-vectors, the so-called 3x2pt analysis, from an $f(R)$ galaxy mock under the incorrect assumption of GR, using for the first time high-fidelity full-sky galaxy mock catalogues. We employ a pair of twin simulations: one with GR and one with Hu--Sawicki $f(R)$ gravity with $|f_{R0}| = 10^{-5}$. The mocks are built using an HOD method to populate the dark matter haloes with galaxies, calibrated against SDSS observations at low redshift. Using conservative scale cuts to minimise modelling uncertainties, we perform 3x2pt analyses and infer cosmological parameters through nested sampling, validating our pipeline with the GR mock. Our results show that when analysing the $f(R)$ galaxy mock assuming GR, the recovered cosmological parameters are very significantly biased, even when considering conservative scale cuts: the Figure of Bias reaches $\sim12\sigma$ for both $\{\Omega_{\rm m}, \sigma_8\}$ and $S_8$. These biases persist even when marginalising over the galaxy bias and baryonic feedback, demonstrating that nuisance parameters cannot absorb the effects of modified gravity. We conclude that incorrectly assuming GR in a universe governed by $f(R)$ gravity leads to severe and detectable biases in cosmological inference for Stage-IV surveys.

astro-ph.CO↗

arXiv2025

Optimising the sample selection for photometric galaxy surveys

Determining cosmological parameters with high precision, as well as resolving current tensions in their values derived from low and high redshift probes, is one of the main objectives of the new generation of cosmological surveys. The combination of complementary probes in terms of parameter degeneracies and systematics is key to achieving these ambitious scientific goals. In this context, determining the optimal survey configuration for an analysis that combines galaxy clustering, weak lensing, and galaxy-galaxy lensing, the so-called 3x2pt analysis, remains an open problem. In this paper, we present an efficient and flexible end-to-end pipeline to optimise the sample selection for 3x2pt analyses in an automated way. Our pipeline is articulated in two main steps: we first consider a self-organising map to determine the photometric redshifts of a simulated galaxy sample. As a proof of method for stage-IV surveys, we use samples from the DESC Data Challenge 2 catalogue. This allows us to classify galaxies into tomographic bins based on their colour phenotype clustering. We then explore different redshift-bin edge configurations for weak lensing only as well as 3x2pt analyses in a novel way. Our method explores multiple configurations of perturbed redshift-bin edges with respect to the fiducial case in an iterative manner. In particular, we sample tomographic configurations for the source and lens galaxies separately. We show that, using this method we quickly converge into an optimised configuration for different numbers of redshift bins and cosmologies. Our analysis demonstrates that for stage-IV surveys an optimal tomographic sample selection can increase the figure of merit of the dark energy (DE) equation of state by a factor of $\sim$2, comparable to an effective increase in survey area of $\sim$4 for non-optimal photometric survey analyses.

astro-ph.CO↗

arXiv2025

A novel test of gravity: Does spacetime geometry track matter density?

We propose a novel test of gravity that combines galaxy clustering with gravitational lensing. In general relativity, the evolution of matter density fluctuations and of the Weyl potential -- the sum of spatial and temporal distortions of the geometry -- are governed by the same growth function. In contrast, alternative theories of gravity that modify the relation between geometry and matter content can lead to differences in these two growths. Exploiting a recent method to directly measure the Weyl potential, we construct a null test that deviates from zero if and only if there is a mismatch between the growth rate of density and that of geometry distortions. We show that changes in the background expansion due to alternative dark energy models and additional forces in the dark matter sector induce no deviations in this test, making it a robust probe for detecting departures from general relativity. Applying the test to current data, we find no evidence of deviation. From an initial $z_*=10$ to $z\sim 0.5$, we constrain the evolution of the Weyl potential to track that of the density to within 33\%. Combining stage-IV surveys will improve the precision across a broad redshift range, limiting differences between the two evolutions to below $2-4\%$.

astro-ph.CO↗

arXiv2025

Probing the Distance Duality Relation with Machine Learning and Recent Data

The distance duality relation (DDR) relates two independent ways of measuring cosmological distances, namely the angular diameter distance and the luminosity distance. These can be measured with baryon acoustic oscillations (BAO) and Type Ia supernovae (SNe Ia), respectively. Here, we use recent DESI DR1, Pantheon+, SH0ES and DES-SN5YR data to test this fundamental relation. We employ a parametrised approach and also use model-independent Generic Algorithms (GA), which are a machine learning method where functions evolve loosely based on biological evolution. When we use DESI and Pantheon+ data without Cepheid calibration or big bang nucleosynthesis (BBN), there is a $2\sigma$ violation of the DDR in the parametrised approach. Then, we add high-redshift BBN data and the low-redshift SH0ES Cepheid calibration. This reflects the Hubble tension since both data sets are in tension in the standard cosmological model $\Lambda$CDM. In this case, we find a significant violation of the DDR in the parametrised case at $6\sigma$. Replacing the Pantheon+ SNe Ia data by DES-SN5YR, we find similar results. For the model-independent approach, we find no deviation in the uncalibrated case and a small deviation with BBN and Cepheids which remains at 1$\sigma$. This shows the importance of considering model-independent approaches for the DDR.

astro-ph.CO↗

arXiv2025

Comparing the motion of dark matter and standard model particles on cosmological scales

Since dark matter particles have never been directly detected, we do not know how they move, and in particular we do not know how they fall inside gravitational potential wells. Usually it is assumed that dark matter only interacts gravitationally with itself and with particles of the standard model, and therefore that its motion is governed by Euler's equation. In this paper, we do test this assumption directly at cosmological scales, by combining measurements of galaxy velocities with measurements of gravitational potential wells, encoded in the Weyl potential. We find that current data are consistent with Euler's equation at redshifts $z\in [0.3,0.8]$, and we place constraints on the strength of a potential fifth force, which would alter the way dark matter particles fall. We find that a positive fifth force cannot exceed 7% of the gravitational interaction strength, while a negative fifth force is limited to 21%. The coming generation of surveys, including the Legacy Survey of Space and Time of the Vera C. Rubin Observatory and the Dark Energy Spectroscopic Instrument will drastically improve the constraints, allowing to constrain a departure from pure gravitational interaction at the level of 2%.

astro-ph.CO↗

arXiv2024

Probing $Λ$CDM through the Weyl potential and machine learning forecasts

For years, the cosmological constant $Λ$ and cold dark matter (CDM) model ($Λ\text{CDM}$) has stood as a cornerstone in modern cosmology and serves as the predominant theoretical framework for current and forthcoming surveys. However, the latest results shown by the Dark Energy Spectroscopic Instrument (DESI), along other cosmological data, show hints in favor of an evolving dark energy. Given the elusive nature of dark energy and the imperative to circumvent model bias, we introduce a novel null test, derived from Noether's theorem, that uses measurements of the Weyl potential (the sum of the spatial and temporal distortion) at different redshifts. In order to assess the consistency of the concordance model we quantify the precision of this null test through the reconstruction of mock catalogs based on $Λ\text{CDM}$ using forthcoming survey data, employing Genetic Algorithms, a machine learning technique. Our analysis indicates that with forthcoming LSST-like and DESI-like mock data our consistency test will be able to rule out several cosmological models at around 4$σ$ and help to check for tensions in the data.

astro-ph.CO↗

arXiv2024

Cosmological measurement of the gravitational constant $G$ using the CMB, the BAO and the BBN

Recent cosmological observations have provided numerous new observations with increasing precision that have led to the era of precision cosmology. The exquisite quality of these observations opens new possibilities towards measuring fundamental constants with good precision and at scales which are complementary to the laboratory ones. In particular, the cosmic microwave background (CMB) temperature and polarization spectra contain a wealth quantity of information, well beyond the basic cosmological parameters. In this paper, we update the precision on a cosmological determination of $G$ by using the latest Planck data release (PR4) in combination with the latest baryon acoustic oscillation (BAO) from the Dark Energy Spectroscopic Instrument (DESI) data release 1 and the primordial Helium fraction from BBN. We demonstrate a precision of $1.8\%$, corresponding to a $\sim25\%$ improvement compared to the literature. This measurement is compatible with laboratory ones within one standard deviation. Finally, we show that this cosmological measurement of $G$ is robust against several assumptions made on the cosmological model, in particular when considering a non-standard dark energy fluid or non-flat models.

astro-ph.CO↗

arXiv2024

$Λ$CDM is alive and well

The $Λ$CDM model faces several tensions with recent cosmological data and their increased accuracy. The mismatch between the values of the Hubble constant $H_0$ obtained from direct distance ladder measurements and from the cosmic microwave background (CMB) is the most statistically significant, but the amplitude of the matter fluctuations is also regarded as a serious concern, leading to the investigation of a plethora of models. We first show that the combination of several recent measurements from local probes leads to a tight constraint on the present-day matter density $Ω_M$ as well as on the amplitude of the matter fluctuations, both acceptably consistent with the values inferred from the CMB. Secondly, we show that the data on cosmic chronometers allow to derive an accurate value of the Hubble constant $H_0$ for $Λ$CDM models: $H_0 = 67.4 \pm 1.34$ km/s/Mpc. This implies that, within $Λ$CDM, some determinations of $H_0$ are biased. Considering a bias on the Hubble constant as a nuisance parameter within $Λ$CDM, we examine such a $Λ$CDM$+ H_0$ bias model on the same statistical grounds as alternative cosmological models. We show that the former statistically supersede most existing extended models proposed up to now. In a third step, we show that the value of $Ω_M$ we obtained, combined with $H_0$ from SH0ES, leads to an accurate measurement of $ω_M$, providing an additional low-redshift test for cosmological models. From this test, most extensions seem to be confronted with a new tension, whereas the $Λ$CDM with $H_0 \sim 67 $ has none. We conclude that a standard $Λ$CDM model with an unknown bias in the Cepheids distance calibration represents a model that reaches a remarkable agreement, statistically better than previously proposed extensions with $H_0 \sim 73 $ for which such a comparison can be performed. (abridged)

astro-ph.CO↗

arXiv2024

Gravitational Redshift Constraints on the Effective Theory of Interacting Dark Energy

Upcoming galaxy surveys provide the necessary sensitivity to measure gravitational redshift, a general relativistic effect that generates a dipole in galaxy clustering data when correlating two distinct populations of galaxies. Here, we study the constraining power of gravitational redshift within the framework of the effective theory of interacting dark energy. This formalism describes linear cosmological perturbations in scalar-tensor theories of gravity with a limited number of free functions, and allows each particle species to be coupled differently to the gravitational sector. In this work, we focus on Horndeski theories with a non-minimal coupling of dark matter to the scalar degree of freedom, yielding a breaking of the weak equivalence principle for this cosmic component, a scenario that is yet untested. We show that the dipole generated by gravitational redshift significantly breaks degeneracies and tightens the constraints on the parameters of the effective theory compared to the standard redshift-space distortion analysis solely based on the even multipoles in the galaxy correlation function, with an improvement of up to $\sim 50\%$ for populations with a galaxy bias difference equal to 1. We make the Python package EF-TIGRE (Effective Field Theory of Interacting dark energy with Gravitational REdshift) developed for this work publicly available.

astro-ph.CO↗

arXiv2024

Testing General Relativity through the $E_G$ Statistic Using the Weyl Potential and Galaxy Velocities

We combine measurements of galaxy velocities from galaxy surveys with measurements of the Weyl potential from the Dark Energy Survey to test the consistency of General Relativity at cosmological scales. Taking the ratio of two model-independent observables - the growth rate of structure and the Weyl potential - we obtain new measurements of the $E_G$ statistic with precision of $6.0-11.3\%$ at four different redshifts. These measurements provide a considerable improvement to past measurements of $E_G$. They confirm the validity of General Relativity at four redshifts, with a deviation of at most $1.6\sigma$ from the predicted values. Contrary to conventional methods that rely on a common galaxy sample with spectroscopic resolution to measure two types of correlations, we directly combine two observables that are independent of the galaxy bias. This provides a novel approach to testing the relation between the geometry of our Universe and the motion of galaxies with improved precision.

astro-ph.CO↗

arXiv2024

A case study for measuring the relativistic dipole of a galaxy cross-correlation with the Dark Energy Spectroscopic Instrument

The data on spectroscopic galaxy clustering collected by the Dark Energy Spectroscopic Instrument (DESI) will allow the significant detection of subtle features in the galaxy two-point correlation in redshift space, beyond the "standard" redshift-space distortions. Here we present an independent assessment of the detectability of the relativistic dipole in the cross-correlation of two populations of galaxies if they would be selected from the Bright Galaxy Survey (BGS) of DESI. We build synthetic galaxy catalogues with the characteristics of the BGS using the light cone of a relativistic $N$-body simulation. Exploring different ways of splitting the populations of galaxies we find that with an unequal split with more bright galaxies than faint galaxies the detectability is significantly boosted, reaching 19 $σ$ in the redshift bin $0.2 \lesssim z \lesssim 0.3$ and expected to be even higher at lower redshift. Moreover, we find that the measured dipole agrees very well with the prediction of relativistic effects from linear theory down to separations of $\sim$ 30 Mpc/$h$.

astro-ph.CO↗

arXiv2023

Measurement of the Weyl potential evolution from the first three years of Dark Energy Survey data

The Weyl potential, which is the sum of the spatial and temporal distortions of the Universe's geometry, provides a direct way of testing the theory of gravity and the validity of the $\Lambda$CDM (Lambda Cold Dark Matter) model. Here we present measurement of the Weyl potential at four redshifts bins using data from the first three years of observations of the Dark Energy Survey. We find that the measured Weyl potential is 2$\sigma$, respectively 2.8$\sigma$, below the $\Lambda$CDM predictions in the two lowest redshift bins. We show that these low values of the Weyl potential are at the origin of the tension between Cosmic Microwave Background measurements and weak lensing measurements, regarding the parameter $\sigma_8$ which quantifies the clustering of matter. Interestingly, we find that the tension remains if no information from the Cosmic Microwave Background is used. Dark Energy Survey data on their own prefer a high value of the primordial fluctuations, together with a slow evolution of the Weyl potential. An important feature of our method is that the measurements of the Weyl potential are model-independent and can therefore be confronted with any theory of gravity, allowing efficient tests of models beyond General Relativity.

astro-ph.CO↗

arXiv2023

Solving the Hubble tension at intermediate redshifts with dynamical dark energy

The current expansion rate of the Universe, the Hubble constant $H_0$, is an important cosmological quantity. However, two different ways to measure its value do not agree -- building a low-redshift distance ladder leads to a higher value of $H_0$ than inferring it from high-redshift observations in a $Λ$CDM cosmology. Most approaches to solve this tension either act at very low redshift by modifying the local distance ladder, or at high redshift by introducing new physics that changes the normalization of the inverse distance ladder. Here we discuss a way to address the Hubble tension at intermediate redshifts instead. By keeping the low- and high-redshift normalizations unchanged, we find a violation of the distance duality in the redshift range where luminosity and angular diameter distances overlap. We 'solve' this problem by introducing a redshift-dependent systematic effect that brings the luminosity distance into agreement with the angular diameter distance. The resulting expansion history is no longer compatible with $Λ$CDM, but this can be fixed with a dynamical dark energy component. In this way, we are able to solve the Hubble tension at intermediate redshifts.

astro-ph.CO↗