arXiv subjects

Gabriela Garcia-Arroyo

Publications and source records attributed to Gabriela Garcia-Arroyo.

13 recordsLinked to original sources

arXiv2026

Early against Late: A contrast on dark energy in the light of DESI DR2

Recent findings from Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation (BAO) measurements, combined with Type Ia supernovae and Cosmic Microwave Background (CMB) data, suggest potential parameter-level deviations from $Λ\text{CDM}$. However, parameter exclusions omit prior-volume penalties, whereas Bayesian evidence uncovers a stark dichotomy between early- and late-time dynamics. To quantify this effect, we perform a Bayesian model comparison that explicitly accounts for the cosmological epoch of dark energy dynamics, contrasting two schemes acting in opposite epochs of cosmic history: pre-recombination Early Dark Energy (EDE) and late-time Chevallier--Polarski--Linder (CPL), both measured against a baseline $Λ$CDM. We validate the learned harmonic-mean estimator against UltraNest (at background level) before applying it to the CMB analysis. Background-only data already disfavor both extensions, yielding {$\ln B_{Λ\text{CDM},\text{EDE}} = 1.48 \pm 0.18$ and $\ln B_{Λ\text{CDM},\text{CPL}} = 2.36 \pm 0.24$}. Including CMB sharpens this result: {EDE is very strongly rejected ($\ln B_{Λ\text{CDM},\text{EDE}} \approx 12.61 \pm 0.17$)} with its early-time fraction constrained to $10^3\,Ω_e^{\rm EDE} = 2.0^{+0.6}_{-1.0}$, whereas CPL remains only mildly disfavored ($\ln B_{Λ\text{CDM},\text{CPL}} \approx 2.34 \pm 0.18$), even though 2D parameter posteriors for both models display a multi-$σ$ deviation from $Λ\text{CDM}$. Thus, Bayesian evidence weakens reported preferences for dark energy dynamics, with the impact depending on the cosmic epoch involved, confirmed by our functional reconstructions of $w_{\rm de}(z)$ and $Ω_{\rm de}(z)$ from posterior samples.

astro-ph.CO↗

arXiv2026

Cosmological Constraints on Interacting Scalar-Field Dark Matter and Early Dark Energy mediated by a Kinetic Kernel

In this work, we build a general framework for constraining interacting scalar fields with cosmological observations, applicable to a broad family of scalar--field potentials and interaction kernels. As a representative example, we derive constraints on a model in which dark matter is described by a scalar field $ϕ$ with a quadratic potential and dark energy by a scalar field $ψ$ with the Albrecht--Skordis potential, considering both the uncoupled case and a more general scenario in which the exchange of energy occurs through an interaction kernel proportional to the kinetic energies of the scalar fields $Q \propto \dotϕ^2 \dotψ^2$. The scalar field parameters are constrained by using \textit{Planck} 2018 CMB data, DESI BAO measurements, Ly-$α$ forest constraints, and SNeIa observations, and we find that the scalar field parameters are driven toward their $Λ$CDM-like limits; the early dark energy fraction is largely suppressed, and the SFDM mass is bounded to values for which the field behaves close to cold dark matter. In the interacting case, the results show no significant preference for the transfer of energy between dark energy and dark matter at 95\% C.L. In general, the model keeps $H_0$ close to the Planck-$Λ$CDM range and provides best-fit $χ^2$ values comparable to those of the corresponding $Λ$CDM fits.

physics.gen-ph↗

arXiv2026

Cosmological Parameter Estimation using Particle Swarm Optimization

The quest for a theoretical framework and ingredients that capture our current understanding of the cosmos has motivated the design of a large number of highly informative experiments, generating an abundant flow of data. Faced with this amount of data and the need for thorough analysis, the main aim of this work is to present and assess the Particle Swarm Optimization (PSO) algorithm as a complementary tool to conventional cosmological data analysis techniques. PSO is one of the most representative bio inspired algorithms, offering strong robustness for high-dimensional or complex problems, while remaining relatively simple to implement and requiring only a few hyperparameters. In this study, we employ two standard variants of the canonical PSO algorithm, global best and local best, to investigate dark energy models using Type Ia Supernovae and Baryon Acoustic Oscillation measurements, focusing in particular on the DESI and DESI+Union3 datasets. Our findings demonstrate that PSO effectively recovers the best fit parameters from observational data and show that, under suitable conditions, PSO can achieve results comparable to those of traditional MCMC techniques but in a significantly reduced computation time. Moreover, the solutions obtained with PSO can be used as high quality initial conditions for MCMC analyzes, thereby accelerating their convergence.

astro-ph.CO↗

arXiv2026

How Holographic is the Dark Energy? A Spline Nodal reconstruction approach

In this work, we explore the generalized holographic dark energy (HDE) scenario. We relate the HDE density to the future-horizon scale via a non-parametric function, which is reconstructed via spline-based nodal interpolation. We perform a Bayesian analysis to assess the model consistency with current observations, including baryon acoustic oscillations (BAO) from the Dark Energy Spectroscopic Instrument (DESI) DR1, Type Ia supernovae (SNe Ia) from the Union3 and Pantheon+ compilations, and local measurements of the Hubble constant, $H_0$, from SH0ES. We show that under specific conditions, the model reduces to $Λ$CDM with one node. We find strong statistical evidence against the standard HDE model, and in contrast, the reconstructed HDE model, with three nodes, provides a better fit to the data than the $Λ$CDM model, indicating a strong statistical preference for the reconstructed model.

astro-ph.CO↗

arXiv2026

Towards a complete scheme of cosmological neutrino self-interactions: Collision term for a wide range of mediator masses

Neutrino self-interactions (NSI) offer a potential pathway to address anomalies in standard cosmology and explain existing cosmological tensions. In this work, we present a novel framework to obtain the neutrino--neutrino collision term within the Boltzmann hierarchy, incorporating both neutrino and mediator masses as free parameters. Our calculations encompass both Dirac-like and Majorana neutrinos and distinguish between two neutrino mass eigenstates. This work provides a valuable tool for future analyses, should a NSI signal be detected. Remarkably, our results show a smooth transition from the light to the heavy mediator approximation as the Universe cools down for non-resonant cases. Thus, for the widely studied heavy mediator, our new scheme eliminates the need to approximate at high redshifts when the temperature increases above the mediator mass, and it provides the tools to test the threshold of validity of the heavy mediator paradigm. While this work focuses on NSI mediated by a scalar particle, the presented framework could be adapted to a broader range of neutrino NSI and possibly to warm dark matter self-interacting scenarios.

hep-ph↗

arXiv2026

Data-driven modeling of rotation curves with artificial neural networks

Galactic rotation curves are crucial for understanding the distribution of mass in galaxies. Despite advances in precision observations, there are discrepancies between the inferred mass from luminosity and the observed rotational velocities, often attributed to dark matter. While traditional parametric models provide valuable insights, they struggle with complex galactic features like prominent bulges and non-circular motions. In this study, we apply artificial neural networks to generate robust, data-driven models, tailored to each galaxy, for the rotation curves of spiral galaxies using high-quality observational data. Our approach demonstrates that neural networks can effectively capture the intricate structure of rotation curves without relying on predefined astrophysical assumptions. By comparing the data-based models with the Navarro-Frenk-White model under two different assumptions for the stellar component, we classify galaxies based on the model that best fits their rotation curves, offering insights into the limitations and strengths of both theoretical and data-based methods. This work highlights the potential of machine learning techniques in identifying galaxies whose dynamics are not well captured by standard theoretical models, pointing to the need for more refined physical descriptions.

astro-ph.GA↗

arXiv2025

Resonant neutrino self-interactions: Insights from the full shape galaxy power spectrum

This paper investigates resonant neutrino self-interactions in cosmology by employing, for the first time, the effective field theory of large-scale structure to model their impact on the matter distribution up to mildly nonlinear scales. We explore a broad range of mediator masses in two main analyses: one combining BOSS Full Shape (FS) galaxy clustering with Big Bang Nucleosynthesis (BBN), and another combining FS with Planck Cosmic Microwave Background (CMB) data. Our results place the strongest cosmological constraints to date on the resonant self interactions when using FS+Planck data, reaching up to $g_ν< 10.8 \times 10^{-14}$ at $95\%$ confidence for the 1 eV mediator. Notably, FS+BBN can constrain the interaction for the 10 eV mediator independently of CMB data, yielding $g_ν< 7.33 \times 10^{-12}$ at $95\%$ confidence. Our results suggest that resonant neutrino self-interactions are unlikely to resolve existing cosmological tensions within the standard $Λ$CDM framework.

astro-ph.CO↗

arXiv2025

Resonant neutrino self-interactions and the $H_0$ tension

In this work, we study the previously unexplored resonant region of neutrino self-interactions. Current disagreement on late and early time observations of the Universe expansion could be solved with new physics acting before the recombination era. Nonstandard neutrino self-interactions are among the most appealing candidates to solve this issue since they could be testable in the near (or midterm) future. We use linear cosmological datasets to test neutrino self-interactions for a sample of fixed scalar mediator masses in the range $10^{-2}$ eV $\leq m_φ\leq 10^{2}$ eV. The resonant behavior produces observable effects at lower couplings than those reported in the literature for heavy and light mediators. We observe that in the best case scenario, using the Planck + BAO dataset, the tension with local measurements of $H_0$ eases from 4.9$σ$ (for $Λ$CDM) down to 2.8$σ$. Albeit, this is driven mainly by the addition of extra radiation, with $ΔN_{\rm eff}\sim 0.5$. The joint dataset which includes Planck, BAO, and $H_0$ prefers a nonzero interaction from 2.3$σ$ to 3.9$σ$ significance in the range $0.5$ eV $\leq m_φ\leq 10$ eV. Although, this last result is obtained with data that are still in tension. These results add the last piece in the parameter space of neutrino self-interactions at the linear perturbation regime.

astro-ph.CO↗

arXiv2024

Interacting Scalar fields: Dark matter and early dark energy

The main aim of this work is to explore the possibility that cold dark matter (CDM) and early dark energy (EDE) can be described by canonical scalar fields that are coupled at the level of its conservation equations. The formalism covers dynamical aspects at the background and linear perturbation levels for an arbitrary coupling function, followed by an example of it. We emphasize the impact of this model on the Matter Power Spectrum and the Cosmic Microwave Background (CMB) spectra, with or without direct interaction. Our findings indicate that the presence of a scalar field can partially counteract the known effects of the other, opening the possibility to avoid some undesired aspects, such as the increase in $Ω_{m}$ that usually is needed in the case of a purely EDE scalar field scenario, in order to fit the CMB spectra. This opens up the possibility to analyzing whether the interaction can help to ameliorate the cosmological tensions.

astro-ph.CO↗

arXiv2024

Coupled Multi Scalar Field Dark Energy

The main aim of this paper is to present the multi scalar field components as candidates to be the dark energy of the universe and their observational constraints. We start with the canonical Quintessence and Phantom fields with quadratic potentials and show that a more complex model should bear in mind to satisfy current cosmological observations. Then we present some implications for a combination of two fields, named as Quintom models. We consider two types of models, one as the sum of the quintessence and phantom potentials and other including an interacting term between fields. We find that adding one extra degree of freedom, by the interacting term, the dynamics enriches considerably and could lead to an improvement in the fit of $-2\lnΔ\Like_{\rm max}= 5.19$, compared to $Λ$CDM. The resultant effective equation of state is now able to cross the phantom divide line, and in several cases present an oscillatory or discontinuous behavior, depending on the interaction value. The parameter constraints of the scalar field models (quintessence, phantom, quintom and interacting quintom) were performed using Cosmic Chronometers, Supernovae Ia and Baryon Acoustic Oscillations data; and the Log-Bayes factors were computed to compare the performance of the models. We show that single scalar fields may face serious troubles and hence the necessity of a more complex models, i.e. multiple fields.

astro-ph.CO↗

arXiv2022

Neutrino mass and kinetic gravity braiding degeneracies

Modified theories of gravity yield an effective dark energy in the background dynamics that achieves an accelerated expansion of the universe. In addition, they present a fifth force that induces gravitational signatures in structure formation, and therefore in the matter power spectrum and related statistics. On the other hand, massive neutrinos suppress the power spectrum at scales that also modified gravity enhances it, so a degeneration of these effects has been recognized for some gravity models. In the present work, we study both effects using kinetic gravity braiding (nKGB) models to find that in spite of some degeneracies, the role of the fifth force at very large scales imprints a bump in the matter power spectrum as a distinctive signature of this model and, therefore, acts as a smoking gun that seems difficult to match within the present knowledge of power spectra. These models result interesting, however, since the n=1 presents no H0 tension, and all nKGB studied here present no sigma8 tension and, in addition, a null neutrino mass is excluded.

astro-ph.CO↗

arXiv2022

Massive neutrino self-interactions with a light mediator in cosmology

Nonstandard self-interactions can alter the evolution of cosmological neutrinos, mainly by damping free streaming, which should leave traces in cosmological observables. Although overall effects are opposite to those produced by neutrino mass and a larger $N_{\rm eff}$, they cannot be totally canceled by these last. We harness cosmological data that includes Cosmic Microwave Background from Plank 2018, BAO measurements, local $H_0$, Ly-$α$ and SNIa, to constrain massive neutrino self-interactions with a very light scalar mediator. We find that the effective coupling constant, at the 95\% C.L., should be $g_{\rm eff}< 1.94 \times 10^{-7}$ for only Planck 2018 data and $1.97\times10^{-7}$ when Planck + BAO are considered. This bound relaxes to $2.27\times 10^{-7}$ ($2.3\times 10^{-7}$) for $H_0$ ($H_0$+SNe+Ly-$α$) data. Using the Planck + BAO dataset, the $H_0$ tension lowers from 4.3$σ$ (for $Λ$CDM) to 3.2$σ$. The Akaike Information Criterion penalizes the self-interacting model due to its larger parameter space for Plank or Planck + BAO data, but favors the interacting model when we use local $H_0$ measurements. A somewhat larger value for $H_0$ is preferred when we include the whole data pool, which comes accompanied with a larger value of $N_{\rm eff}$ and a more constricted bound on $Σm_ν$.

astro-ph.CO↗

arXiv2020

Effects of Dark Energy anisotropic stress on the matter power spectrum

We study the effects of dark energy (DE) anisotropic stress on features of the matter power spectrum (PS). We employ the Parametrized Post-Friedmannian (PPF) formalism to emulate an effective DE, and model its anisotropic stress properties through a two-parameter equation that governs its overall amplitude ($g_0$) and transition scale ($c_g$). For the background cosmology, we consider different equations of state to model DE including a constant $w_0$ parameter, and models that provide thawing (CPL) and freezing (nCPL) behaviors. We first constrain these parameters by using the Pantheon, BAO, $H_0$ and CMB Planck data. Then, we analyze the role played by these parameters in the linear PS. In order for the anisotropic stress not to provoke deviations larger than $10\%$ and $5\%$ with respect to the $Λ$CDM PS at $k \sim 0.01 \,h/\text{Mpc}$, the parameters have to be in the range $-0.30< g_0 < 0.32$, $0 \leq c_g^2 < 0.01$ and $-0.15 < g_0 < 0.16$, $0 \leq c_g^2 < 0.01$, respectively. Additionally, we compute the leading nonlinear corrections to the PS using standard perturbation theory in real and redshift space, showing that the differences with respect to the $Λ$CDM are enhanced, especially for the quadrupole and hexadecapole RSD multipoles.

astro-ph.CO↗