arXiv subjects

Noemi Frusciante

Publications and source records attributed to Noemi Frusciante.

At least 19 recordsLinked to original sources

arXiv2026

N-body Simulations of Large-Scale Structure in the Generalized Cubic Covariant Galileon Model

We present the first N-body simulations of structure formation in the Generalized Cubic Covariant Galileon (GCCG) model. This theory extends the cubic covariant Galileon through power-law kinetic and cubic derivative interactions and admits tracker solutions leading to late-time cosmic acceleration. Previous studies of GCCG have mostly focused on the background, linear perturbations, or semi-analytic nonlinear prescriptions. Here we implement the nonlinear scalar-field equation in the ECOSMOG adaptive-mesh refinement code, allowing us to follow the coupled evolution of matter clustering and Vainshtein screening in the fully nonlinear regime. We quantify the impact of GCCG on the nonlinear matter power spectrum and compare the simulation results with predictions from the halo-model reaction approach. For the parameter choices considered, the GCCG model enhances the matter power spectrum relative to the corresponding QCDM cosmology, with the effect increasing towards low redshift and reaching approximately $7\%$ at $z=0$ in the transition to the nonlinear regime. At smaller scales, the enhancement decreases as a consequence of Vainshtein screening. We find that the reaction framework captures the qualitative behaviour of the simulations, while residual differences appear on deeply nonlinear scales. We also analyse the abundance of dark matter haloes, finding an enhancement relative to QCDM that becomes more pronounced towards lower redshift and in the high-mass tail. These simulations provide the first nonlinear calibration of structure formation in GCCG and establish the range of validity of efficient semi-analytical predictions for applications to forthcoming large-scale-structure surveys.

astro-ph.CO↗

arXiv2026

Can cosmic voids ease the Hubble tension? Local expansion in $w_0w_a$CDM

We investigate the effect of local cosmic voids on low-redshift measurements of the Hubble rate in flat $w_0w_a$CDM cosmologies. Using a hydrodynamical model for isolated spherical inverse top-hat underdensities, we compute the void-induced Hubble shift as a function of redshift, enclosed density contrast $δ_{\rm E}$ and cosmological parameters. We find that the effect is mainly controlled by the matter sector, through $δ_{\rm E}$ and $Ω_{\rm m,0}$, while dynamical dark energy gives only subdominant late-time corrections. For a Planck-calibrated $Λ$CDM background, matching the SH0ES value requires a present-day void with $δ_{\rm E}(z=0)\simeq -0.44$, substantially deeper than the KBC-like local underdensity. A KBC-like void lowers the SH0ES-Planck discrepancy to about $2σ$, but is not deep enough to fully reconcile the two measurements. Allowing for dynamical dark energy, including regions motivated by recent DES and DESI analyses, changes this result only at the percent level. We also show that the reported redshift dependence of locally inferred $H_0$ values can be represented phenomenologically by an effective enclosed matter profile. This reconstruction should be interpreted as a consistency test of local-structure effects rather than as explanation for an evolving background value of $H_0$. Overall, local underdensities can affect low-redshift Hubble-rate inferences, but they do not resolve the Hubble tension within the spherical void setup considered here.

astro-ph.CO↗

arXiv2026

Cosmic voids evolution in modified gravity via hydrodynamics

We present a hydrodynamical description of isolated spherical voids in modified gravity (MG), extending the standard General Relativity (GR) and dynamical dark energy treatment by encoding gravity modifications into effective couplings that enter the Euler and Poisson equations. This yields a compact non-linear evolution equation for the Eulerian density contrast, controlled by a time- and density-dependent effective gravitational strength, and provides a direct map between model functions and void observables. We apply the framework to the luminal Galileon class of models, where derivative self-interactions generate Vainshtein screening and might lead to a breakdown of the physical branch in sufficiently underdense regions. Exploiting this feature, we apply the void-informed viability requirement that translates into bounds on the theory parameter space and, equivalently, on the minimum attainable void depth as a function of redshift. For viable parameters of a concrete model, we quantify the impact of MG on isolated void evolution, the Lagrangian to Eulerian mapping, and the shell-crossing threshold. Relative to GR, we find a clear hierarchy of MG effects, with ${\cal O}(10\%)$ modifications in the gravitational couplings, percent-level shifts in the void density evolution, and sub-percent deviations in both the mapping and the shell-crossing thresholds. Moreover, within the adopted parametrization, we show analytically that voids always lie in an unscreened regime on the physical branch. Overall, the formalism provides a self-consistent route to predict void dynamics and consistency constraints in a broad class of MG models.

astro-ph.CO↗

arXiv2026

How deep can a cosmic void be? Voids-informed theoretical bounds in Galileon gravity

We establish a void-based consistency test for Galileon scalar-tensor theories. We show that the previously reported unphysical breakdown of the predicted Newtonian force in certain Galileon models is controlled by a single condition linking non-linear void dynamics to the cosmic expansion history. This connection yields a redshift-dependent upper bound on the allowed depth of voids and promotes this requirement to a new viability condition, complementary to standard stability criteria. As an example, we apply this void-based criterion to a linear parameterization in the scale factor constrained by theoretical and observational bounds; we find that $\sim 60\%$ of the parameter space is excluded, with most problematic models failing by $z\lesssim 10$. These results position cosmic voids as sharp, complementary and theory-informed filters for viable modified gravity, enabling more informed priors and parameter-space choices in future cosmological inference.

astro-ph.CO↗

arXiv2026

Inverse non-metricity in $f(Q)$ gravity: cosmology and observational constraints

We study a minimal modified gravity scenario in the symmetric teleparallel (non-metricity) formulation, focusing on an inverse non-metricity term with $f(Q)=Q+M^4 Q^{-1}$. The model does not introduce additional free parameters relative to $Λ$CDM, but modifies the late-time expansion and linear growth via an enhanced effective gravitational coupling. We identify key signatures: an enhanced matter power spectrum and CMB lensing, alongside a reduced late-time ISW effect and a shift in CMB peak positions. We confront the model with CMB data alone and in combination with BAO, RSD, SNIa, and DES large-scale structure data, considering both fixed minimal neutrino mass and varying $Σm_ν$. We find that the model typically prefers higher $H_0$ than $Λ$CDM, alleviating the $H_0$ tension, while its boosted growth tends to increase clustering amplitudes unless offset by larger neutrino masses when $Σm_ν$ is free. Overall, CMB-only data provide at most weak statistical support compared to $Λ$CDM, whereas late-time measurements impose tight restrictions that largely remove any improvement, positioning this model as a minimal yet strongly constrained alternative to dark energy.

astro-ph.CO↗

arXiv2026

$\mathcal{H}$-EFTCAMB: A Cobaya-Integrated, Python-Wrapped Extension of EFTCAMB for Covariant Horndeski Gravity

We present $\mathcal{H}\mathtt{-EFTCAMB}$, the official successor to $\mathtt{EFTCAMB}$. The original $\mathtt{EFTCAMB}$ is designed as a consistent and numerically stable implementation of the effective field theory (EFT) of dark energy in the Einstein-Boltzmann code $\mathtt{CAMB}$. On top of this, $\mathcal{H}\mathtt{-EFTCAMB}$ introduces a new Horndeski module that supports computing cosmology for an arbitrary input covariant Horndeski Lagragian. $\mathcal{H}\mathtt{-EFTCAMB}$ supports both mapping the Horndeski theory to an EFT lagrangian to solve in the EFT framework as well as directly solving for the scalar field equations of motion derived from the covariant Lagrangian. The latter approach also works for the cases when the Horndeski field experiences turn-overs, e.g. oscillation, where the EFT approach breaks down. The Horndeski module has been validated by comparing internally with existing models in the original $\mathtt{EFTCAMB}$ and externally with $\mathtt{hi\_class}$. $\mathcal{H}\mathtt{-EFTCAMB}$ features a flexible Python wrapper that is seamlessly integrated into the widely utilized cosmological sampler $\mathtt{Cobaya}$. \heft~is publicly available and serves as a comprehensive tool for testing gravity against the precision data from current and next-generation surveys.

gr-qc↗

arXiv2026

A spherical hydrodynamical model of cosmic voids in ΛCDM and beyond

Cosmic voids have emerged as powerful probes for cosmology, providing complementary information on the large-scale structure of the universe. We present the first application of a hydrodynamical framework to model the evolution of cosmic voids. This approach offers a physically intuitive characterization of void dynamics and can naturally be applied to non-standard cosmologies. We derive the cosmology-dependent mapping that relates the linear (Lagrangian) and fully non-linear (Eulerian) evolution of the matter density contrast, a central component for accurate theoretical modeling of void statistics. Furthermore, we present a new method for determining the shell-crossing epoch across arbitrary cosmological backgrounds, thereby extending previous treatments restricted to the Einstein-de Sitter universe. Motivated by recent DESI results hinting at dynamical dark energy, we investigate void evolution in $ w_0w_a$CDM cosmologies by varying $ w_0$ and $w_a$. We also consider the impact of varying the matter density parameter, $ Ω_{\mathrm{m},0}$. We find that the evolution of isolated, spherically symmetric cosmic voids is most sensitive to $ Ω_{\mathrm{m},0} $ and $ w_0 $, which can alter the non-linear density contrast by up to 20-30%. Variations in $w_a$ have a smaller impact, but may still lead to measurable effects. We also show that the cosmology-dependent mapping between linear and non-linear density contrasts may provide a sensitive probe of dynamical dark energy in precision void analyses.

astro-ph.CO↗

arXiv2024

Matter Power Spectra in Modified Gravity: A Comparative Study of Approximations and $N$-Body Simulations

Testing gravity and the concordance model of cosmology, $Λ$CDM, at large scales is a key goal of this decade's largest galaxy surveys. Here we present a comparative study of dark matter power spectrum predictions from different numerical codes in the context of three popular theories of gravity that induce scale-independent modifications to the linear growth of structure: nDGP, Cubic Galileon and K-mouflage. In particular, we compare the predictions from full $N$-body simulations, two $N$-body codes with approximate time integration schemes, a parametrised modified $N$-body implementation and the analytic halo model reaction approach. We find the modification to the $Λ$CDM spectrum is in $2\%$ agreement for $z\leq1$ and $k\leq 1~h/{\rm Mpc}$ over all gravitational models and codes, in accordance with many previous studies, indicating these modelling approaches are robust enough to be used in forthcoming survey analyses under appropriate scale cuts. We further make public the new code implementations presented, specifically the halo model reaction K-mouflage implementation and the relativistic Cubic Galileon implementation.

astro-ph.CO↗

arXiv2024

Non-linear power spectrum and forecasts for Generalized Cubic Covariant Galileon

To fully exploit the data from next generation surveys, we need an accurate modelling of the matter power spectrum up to non-linear scales. Therefore in this work we present the halo model reaction framework for the Generalized Cubic Covariant Galileon (GCCG) model, a modified gravity model within the Horndeski class of theories which extends the cubic covariant Galileon (G3) by including power laws of the derivatives of the scalar field in the K-essence and cubic terms. We modify the publicly available software ReACT for the GCCG in order to obtain an accurate prediction of the non-linear power spectrum. In the limit of the G3 model we compare the modified ReACT code to $N$-body simulations and we find agreement within 5\% for a wide range of scales and redshifts. We then study the relevant effects of the modifications introduced by the GCCG on the non-linear matter power spectrum. Finally, we provide forecasts from spectroscopic and photometric primary probes by next generation surveys using a Fisher matrix method. We show that future data will be able to constrain at 1$σ$ the two additional parameters of the model at the percent level and that considering non-linear corrections to the matter power spectrum beyond the linear regime is crucial to obtain this result.

astro-ph.CO↗

arXiv2024

Cosmological study of a symmetric teleparallel gravity model

We study a symmetric teleparallel gravity with a Lagrangian of logarithmic form. The full model leads to an accelerated universe and for specific values of the free parameters the Hubble rate reduces to the well-known Dvali-Gabadadze-Porrati model, though the evolution of the gravitational potentials are different. We consider different branches of the logarithmic model, among which are self-accelerated branch and normal branch. The phenomenology of both the background and linear perturbations is discussed, including all the relevant effects on cosmic microwave background radiation (CMB) angular power spectrum, lensing and matter power spectra. To this purpose, we modified the Einstein-Boltzmann code mgcamb. Finally, we derive bounds on the free parameters which are in agreement with early dark energy constraint from CMB and big bang nucleosynthesis constraint on the helium abundance.

gr-qc↗

arXiv2024

Phenomenology of Horndeski Gravity under Positivity Bounds

A set of conditions that any effective field theory needs to satisfy in order to allow for the existence of a viable UV completion has recently gained attention in the cosmological context under the name of $\textit{positivity bounds}$. In this paper we revisit the derivation of such bounds for Horndeski gravity and translate them into a complete set of viability conditions in the language of effective field theory of dark energy. We implement the latter into $\texttt{EFTCAMB}$ and explore the large scale structure phenomenology of Horndeski gravity under positivity bounds. We build a statistically significant sample of viable Horndeski models, and derive the corresponding predictions for the background evolution, in terms of $w_{\rm DE}$, and the dynamics of linear perturbations, in terms of the phenomenological functions $μ$ and $Σ$, associated to clustering and weak lensing, respectively. We find that the addition of positivity bounds to the traditional no-ghost and no-gradient conditions considerably tightens the theoretical constraints on all these functions. The most significant feature is a strengthening of the correlation $μ\simeqΣ$, and a related tight constraint on the luminal speed of gravitational waves $c^2_T\simeq1$. In anticipation of a more complete formulation of positivity conditions in cosmology, this work demonstrates the strong potential of such bounds in shaping the viable parameter space of scalar-tensor theories.

astro-ph.CO↗

arXiv2024

Spherical collapse and halo abundance in shift-symmetric Galileon theory

We present the nonlinear growth of bound cosmological structures using the spherical collapse approach in the shift-symmetric Galileon theories. In particular, we focus on the class of models belonging to the Kinetic Gravity Braiding by adopting a general parametrization of the action encoding a large set of models by means of four free parameters: two defining the background evolution and two affecting the perturbations. For the latter we identify their specific signatures on the linearised critical density contrast, nonlinear effective gravitational coupling and the virial overdensity and how they drive their predictions away from $Λ$CDM. We then use the results of the spherical collapse model to predict the evolution of the halo mass function. We find that the shift-symmetric model predicts a larger number of objects compared to $Λ$CDM for masses $M \gtrsim 10^{14} h^{-1} \mathrm{M}_\odot$ and such number increases for larger deviations from the standard model. Therefore, the shift-symmetric model shows detectable signatures which can be used to distinguish it from the standard scenario.

astro-ph.CO↗

arXiv2023

Forecasts on interacting dark energy with standard sirens

We present the predictions with standard sirens at Gravitational Waves detectors, such as the Laser Interferometer Space Antenna (LISA) and the Einstein Telescope (ET), for interacting dark energy theories. We focus on four models characterised by couplings between the dark energy field and the dark matter fluid arising from conformal or disformal transformations of the metric, along with an exponential self-interacting potential. To this purpose we construct mock catalogues and perform a Markov Chain Monte Carlo analysis by considering ET and LISA standard sirens, and also their combination with Baryon Acoustic Oscillations (BAO) and Supernovae Ia (SNIa) data. We find that in all the four models considered, the accuracy on the $H_0$ parameter increases by one order of magnitude at 1$σ$ when compared to the SNIa+BAO data set, possibly shedding light in the future on the origin of the $H_0$-tension. The combination of standard sirens with SNIa+BAO allows to improve the accuracy on some coupling and exponential parameters, hinting at future prospects for constraining interactions in the dark sector.

astro-ph.CO↗

arXiv2023

$f(Q)$-gravity and neutrino physics

Within the $f(Q)$-gravity framework we perform a phenomenological study of the cosmological observables in light of the degeneracy between neutrinos physics and the modified gravity parameter and we identify specific patterns which allow to break such degeneracy. We also provide separately constraints on the total mass of the neutrinos, $Σm_ν$, and on the effective number of neutrino species, $N_{\rm eff}$, using cosmic microwave background (CMB), baryon acoustic oscillation (BAO), redshift space distortion (RSD), supernovae (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. The strongest upper bound on the total mass of the neutrinos is found for the combination of CMB+BAO+RSD+SNIa and it is $Σm_ν<0.277$ eV at 95\% C.L. For the same combination of data we find $N_{\rm eff}=2.93^{+0.31}_{-0.34}$ at 95\% C.L. We also find that all combinations of data we consider, prefer a stronger gravitational interaction than $Λ$CDM. Finally, we consider the $χ^2$ and deviance information criterion statistics and find the $f(Q)+Σm_ν$ model to be statistically supported by data over the standard scenario. On the contrary $f(Q)+N_{\rm eff}$ is supported by CMB+BAO+RSD+SNIa but a moderate evidence against it is found with GC and WL data.

astro-ph.CO↗

arXiv2023

Modified Gravity and Cosmology: An Update by the CANTATA Network

General Relativity and the $Λ$CDM framework are currently the standard lore and constitute the concordance paradigm. Nevertheless, long-standing open theoretical issues, as well as possible new observational ones arising from the explosive development of cosmology the last two decades, offer the motivation and lead a large amount of research to be devoted in constructing various extensions and modifications. All extended theories and scenarios are first examined under the light of theoretical consistency, and then are applied to various geometrical backgrounds, such as the cosmological and the spherical symmetric ones. Their predictions at both the background and perturbation levels, and concerning cosmology at early, intermediate and late times, are then confronted with the huge amount of observational data that astrophysics and cosmology are able to offer recently. Theories, scenarios and models that successfully and efficiently pass the above steps are classified as viable and are candidates for the description of Nature. This work is a Review of the recent developments in the fields of gravity and cosmology, presenting the state of the art, high-lighting the open problems, and outlining the directions of future research. Its realization was performed in the framework of the COST European Action ``Cosmology and Astrophysics Network for Theoretical Advances and Training Actions''.

gr-qc↗

arXiv2022

Dissecting kinetically coupled quintessence: phenomenology and observational tests

We investigate an interacting dark energy model which allows for the kinetic term of the scalar field to couple to dark matter via a power-law interaction. The model is characterised by scaling solutions at early times, which are of high interest to alleviate the coincidence problem, followed by a period of accelerated expansion. We discuss the phenomenology of the background evolution and of the linear scalar perturbations and we identify measurable signatures of the coupling in the dark sector on the cosmic microwave background, the lensing potential auto-correlation and the matter power spectra. We also perform a parameter estimation analysis using data of cosmic microwave background temperature, polarisation and lensing, baryonic acoustic oscillations and supernovae. We find that the strength of the coupling between the dark sectors, regulated by the parameter $α$, is constrained to be of order $10^{-4}$. A model selection analysis does not reveal a statistical preference between $Λ$CDM and the Kinetic model.

astro-ph.CO↗

arXiv2022

Report of the Topical Group on Cosmic Probes of Fundamental Physics for for Snowmass 2021

Cosmic Probes of Fundamental Physics take two primary forms: Very high energy particles (cosmic rays, neutrinos, and gamma rays) and gravitational waves. Already today, these probes give access to fundamental physics not available by any other means, helping elucidate the underlying theory that completes the Standard Model. The last decade has witnessed a revolution of exciting discoveries such as the detection of high-energy neutrinos and gravitational waves. The scope for major developments in the next decades is dramatic, as we detail in this report.

hep-ph↗

arXiv2022

Probing Modified Gravity with Integrated Sachs-Wolfe CMB and Galaxy Cross-correlations

We use the cross-correlation power spectrum of the integrated Sachs-Wolfe (ISW) effect in the cosmic microwave background (CMB) temperature anisotropy and galaxy fluctuations to probe the physics of late-time cosmic acceleration. For this purpose, we focus on three models of dark energy that belong to a sub-class of Horndeski theories with the speed of gravity equivalent to that of light: Galileon Ghost Condensate (GGC), Generalized Cubic Covariant Galileon (GCCG), and K-mouflage. In the GGC and GCCG models, the existence of cubic-order scalar self-interactions allows a possibility for realizing negative ISW-galaxy cross-correlations, while the K-mouflage model predicts a positive correlation similar to the $Λ$-cold-dark-matter (LCDM) model. In our analysis, we fix the parameters of each model to their best-fit values derived from a baseline likelihood analysis with observational data from CMB, baryon acoustic oscillations, and supernovae type Ia. Then we fit those best-fit models to the ISW-galaxy cross-correlation power spectrum extracted from a collection of photometric redshift surveys. We find that both GGC and GCCG best-fit models degrade the fit to the ISW-galaxy cross-correlation data compared to LCDM best-fit model. This is attributed to the fact that, for their best-fit values constrained from the baseline likelihood, the cubic-order scalar self-interaction gives rise to suppressed ISW tails relative to $Λ$CDM. The K-mouflage best-fit model is largely degenerate with the LCDM best-fit model and has a positively correlated ISW-galaxy power close to that of LCDM.

astro-ph.CO↗