arXiv subjects

Miguel A. García-Aspeitia

Publications and source records attributed to Miguel A. García-Aspeitia.

At least 19 recordsLinked to original sources

arXiv2026

Constraining a model supported in Moiré gravity with a recent data release

Moiré theory is a revolutionary alternative arising from solid-state physics that can be extended to gravity, forming a framework called Moiré gravity. The idea behind it is that Einsteinian gravity has a validity limit and must be extended to Moiré gravity, in which the Friedmann equation changes and a new scalar field emerges. In this vein, in this paper, we propose an analytic solution for the Moiré scalar field coupled with the modified Friedmann equation, studying the viability and constraining the value for the main parameter of the scalar field and cosmology in general, through the use of datasets that contain cosmic chronometers, type Ia supernovae, intermediate-luminosity quasars, and hydrogen II galaxies. Our results allow for an accelerated phase with two peaks, but also predict an extremely decelerated stage, with $q(z=0)=15.376^{+6.403}_{-4.692}$ when the characteristic parameter of the theory is $\jmath=0.677^{+0.001}_{-0.002}$, in contrast to other models that decelerate at $z=0$.

physics.gen-ph↗

arXiv2026

A comparative study of emergent dark energy models

Late (emergent) dark energy models that involve a hyperbolic tangent in their dynamic equations have achieved success due to their simplicity, the possibility of resolving the Hubble tension, and, in some cases their consistency with the Dark Energy Spectroscopic Instrument (DESI) results. Among the most studied are the Phenomenological and General Emergent Dark Energy Models (PEDE and GEDE, respectively), the variable curvature model, and the graduated dark energy model. Our goal is to include the curvature term in the models and perform a robust comparative study using diverse data samples, in particular, Cosmic Chronometers, Type Ia supernovae, Baryon Acoustic Oscillations from DESI-DR1, and Cosmic Microwave Background Radiation. This study presents the Universe age, the deceleration, the $w_{eff}$ parameter reconstruction, the redshift transition, and the best fit for the free parameters of each model. Our collected evidence from Akaike Information Criterion and Bayesian Information Criterion indicates that the best candidate is the PEDE model. Nevertheless, the variable-curvature model is the only model that exhibits a decelerated phase near $z=0$, consistent with the results from DESI.

astro-ph.CO↗

arXiv2026

Reconstructing the cosmic expansion with a generalized q(z) parameterization: A decelerating Universe from late-time constraints

We present a generalized phenomenological parameterization of the deceleration parameter $q(z)$ that incorporates an effective radiative component (ERC) in addition to a localized late-time contribution. The proposed framework extends previous two-parameter $q(z)$ reconstructions by explicitly regulating the high-redshift behavior while preserving the late-time transition dynamics. We constrain the free parameters $(h, q_0, z_c, z_e)$ using late-time observational data from cosmic chronometers (CC), Pantheon+ Type Ia supernovae (SNIa), H\,\textsc{ii} galaxies (HIIG), and intermediate-luminosity quasars (QSO). For the full data combination (CC+SNIa+HIIG+QSO), we obtain $q_0 = -0.25^{+0.04}_{-0.04}$ and a transition redshift $z_T \simeq 0.80$, indicating a currently accelerating Universe with a transition occurring earlier than in the $Λ$CDM model. Within the redshift range probed by the data, the reconstructed $q(z)$ deviates from the $Λ$CDM trend, suggesting a possible reduction of the late-time acceleration. Furthermore, the reconstruction favors a relatively high value of the Hubble parameter, $h = 0.729 \pm 0.006$. The ERC remains weakly constrained by late-time data but ensures a smooth and monotonic evolution of $q(z)$, $j(z)$, and $w_{\rm eff}(z)$ across a wide redshift range. Within the observed interval, the model effectively reproduces the late-time behavior of the previous parametrization, while providing a controlled extension toward early epochs. Our results show that current low- and intermediate-redshift data are compatible with a reduced late-time acceleration.

astro-ph.CO↗

arXiv2026

Late-Time Cosmic Acceleration from QCD Confinement Dynamics

We explore a phenomenological extension of the Polyakov-Nambu-Jona-Lasinio (PNJL) model by introducing a curvature-sensitive effective contribution to the Polyakov loop potential, motivated by the hypothesis that the non-perturbative QCD vacuum in the confined phase may retain a residual sensitivity to cosmic expansion. In a spatially flat FLRW background, this modification reduces to a term proportional to $α(H/H_0)^d f(Φ, Φ^*)$, which naturally vanishes in the deconfined regime and behaves as an effective dynamical vacuum component at late times, without invoking a fundamental cosmological constant. The construction provides an effective thermodynamic description of the QCD sector within an adiabatic framework and introduces a minimal phenomenological extension characterized by the exponent $d$ and the amplitude parameter $α$. We analyze the cosmological implications at the background level and confront the model with low-redshift observations, including cosmic chronometers, Type Ia supernovae, HII galaxies, and quasars. Using Bayesian Monte Carlo techniques, we constrain the model parameters and compare its performance with $Λ$CDM. Our results indicate that the modified PNJL cosmology provides a statistically competitive fit to current data while allowing small departures from $Λ$CDM within observational uncertainties. We also investigate the impact of the coupling on the QCD phase diagram and the critical end point. The framework offers a tractable effective approach to connect confinement physics with late-time cosmology and suggests directions for further theoretical development in QCD under curved backgrounds.

physics.gen-ph↗

arXiv2025

$w_{dm}$-$w_{de}$ cosmological model with new data samples of cosmological observations

We revisit a cosmological model where dark matter (DM) and dark energy (DE) follow barotropic equations of state, allowing deviations from the standard $Λ$CDM framework (i.e. $w_{dm} \neq 0$, $w_{de} \neq -1$), considering both flat and non-flat curvature. Using a dynamical system approach, we identify equilibrium states that govern stability, expansion, and contraction. Expansion occurs when $H>0$, while contraction is linked to $H < 0$. Accelerated expansion arises from DE dominance, whereas radiation- and matter-dominated phases lead to deceleration. Some solutions are unphysical due to density constraints, but viable cases offer insights into cosmic transitions, including the Einstein static universe, which allows for shifts between accelerating and decelerating phases. We perform a Bayesian analysis with updated datasets, including observational Hubble data, Pantheon+ Type Ia supernovae, strong lensing systems, baryon acoustic oscillations and cosmic microwave background, to constrain the parameters $w_{dm}$ and $w_{de}$. Our results from the data joint analysis show consistency with $Λ$CDM within $3σ$, but none of the cases reproduce $w_{dm} = 0$ and $w_{de} = -1$. Nevertheless, the comparison with the standard model using the Akaike and Bayesian information criteria indicates that only the non-flat scenario has the potential to be competitive. This suggests that a non-dust-like DM may impact structure formation, while DE could shift toward quintessence fluid. While $Λ$CDM remains a strong model, our findings indicate that alternative dark sector models with non-standard EoS could be viable and offer new insights into cosmic evolution.

astro-ph.CO↗

arXiv2025

DESI and fast radio burst used to constrain modified theories of gravity

This paper is devoted to the study of the viability of DESI and the fast radio burst to constrain the free parameters of modified theories of gravity. Thus, we present a model supported in $f(R)$ gravity involving a function of the Ricci scalar named Starobinsky-type with the peculiarity that the non-commutative essence is intrinsic to the coefficients. Additionally, to understand the dynamics within a flat Friedmann-Lemaitre-Robertson-Walker universe, we explore the possibility of deriving a Friedman equation (in measure) that results from an adequate mathematical treatment. As we mentioned previously, to test the outlined model, a Monte Carlo Markov chain analysis is implemented, using cosmic chronometers, type Ia supernovae, Hydrogen II galaxies, Intermediate-luminosity quasars, Baryon Acoustic oscillations and Fast Radio Bursts data, to constraint the free parameters of the model and presenting $H(z)$, $q(z)$ and $ω_{eff}(z)$. The final results are compared with the $Λ$CDM model and a robust discussion is presented about the viability of DESI and fast radio burst to constraint free parameters in specific to a modified theory of gravity.

astro-ph.CO↗

arXiv2025

On a model of variable curvature that mimics the observed Universe acceleration

We present a new model based on General Relativity in where a subtle change of curvature at late times is able to produce the observed Universe acceleration and an oscillating behavior in the effective equation of state. This model aims to test the cosmological principle, by introducing a slight modification in the traditional FLRW metric, through a non-constant curvature parameter. This model is defined by a smooth step-like function with a slight transition between two curvature values, fulfilling the premise that the derivative of this curvature parameter is preserved as approximately zero, $\dotκ\approx0$. To test our model, we implemented a MCMC likelihood analysis using Cosmic Chronometers and Type Ia supernovae data in order to constrain the free parameters of the model and reconstruct $H(z)$, $q(z)$, $w_{eff}(z)$, also comparing the results with the $Λ$CDM model. The main result is that this model provides an alternative to the acceleration of the Universe without the need of a dark energy component. In particular, it gives an equivalent phase transition at $z \sim 0.5$, while obtaining the same fraction of matter density, similar to what is expected for the standard $Λ$CDM model. Remarkably, it also predicts a slight decelerated state at $z=0$ in agreement with diverse Dark Energy parameterizations. We conclude that the behavior of our proposed model points towards a new and intriguing way to investigate slight violations to the cosmological principle, in particular the case of inhomogenities during low phase transitions.

astro-ph.CO↗

arXiv2024

Phenomenological emergent dark energy in the light of DESI Data Release 1

This manuscript revisits the phenomenological emergent dark energy model (PEDE) by confronting it with recent cosmological data from early and late times. In particular we analyze PEDE model by using the baryon acoustic oscillation (BAO) measurements coming from both Dark Energy Spectroscopy Instrument (DESI) data release 1 and Sloan Digital Sky Survey (SDSS). Additionally, the measurements from cosmic chronometers, supernovae type Ia (Pantheon+), quasars, hydrogen II galaxies and cosmic background radiation distance priors are considered. By performing a Bayesian analysis based on Monte Carlo Markov Chain, we find consistent results on the constraints when SDSS and DESI are considered. However, we find higher values on the Hubble constant than Supernova $H_0$ for the Equation of State (SH0ES) does although it is still in agreement, within $1σ$ confidence level, when BAO measurements are added. Furthermore, we estimate the age of the Universe younger $\sim3\%$ than the one predicted by the standard cosmology. Additionally, we report values of $q_0 = -0.771^{+0.007}_{-0.007}$, $z_T = 0.764^{+0.011}_{-0.011}$ for the deceleration parameter today and the deceleration-acceleration transition redshift, respectively. However, PEDE cosmology is disfavoured by the combined samples.

astro-ph.CO↗

arXiv2024

General perturbations in D+1 standard and brane cosmology revisited

In the present work, we generalize the theory of perturbations in a D + 1 dimensional space-time with cosmological constant, studying scalar, vector and tensor perturbations, as well as its structure in Newtonian and Synchronous gauge. We also show the theory of perturbations in the context of brane cosmology, where branes are embedded in a set of D-spatial dimensions, a temporal dimension, and an additional spatial dimension. In both, standard and brane cosmology an unperturbed spacetime is provided with a Friedmann-Lemaitre-Robertson-Walker metric and arbitrary sectional curvature, the matter content has the shape of a perfect fluid. In addition, we consider the arbitrary sectional curvature, obtaining the respective equations in the Newtonian and Synchronous gauge. We highlight that the results presented in this article can be used to treat brane cosmology with two concentric branes or tackle the σ_{8} tension with a braneworld approach. Finally, as an example of the utility of all the technology presented in this paper, we show an application to the energy ux and the repercussions in the framework of the brane-worlds.

gr-qc↗

arXiv2024

Synchronize your \textit{chrono-brane}: Testing a variable brane tension model with strong gravitational lensing

Brane world models have shown to be promising to understand the late cosmic acceleration, in particular because such acceleration can be naturally derived, mimicking the dark energy behaviour just with a five dimensional geometry. In this paper we present a strong lensing joint analysis using a compilation of early-type galaxies acting as a lenses, united with the power of the well studied strong lensing galaxy cluster Abell\,1689. We use the strong lensing constraints to investigate a brane model with variable brane tension as a function of the redshift. In our joint analysis we found a value $n = 7.8^{+0.9}_{-0.5}$, for the exponent related to the brane tension, showing that $n$ deviates from a Cosmological Constant (CC) scenario (n=6). We obtain a value for the deceleration parameter, $q(z)$ today, $q(0)=-1.2^{+0.6}_{-0.8}$, and a transition redshift, $z_t=0.60\pm0.06$ (when the Universe change from an decelerated phase to an accelerated one). These results are in contrast with previous work that favors CC scenario, nevertheless our lensing analysis is in agreement with a formerly reported conclusion suggesting that the variable brane tension model is able to source a late cosmic acceleration without an extra fluid as in the standard one.

astro-ph.CO↗

arXiv2023

MeV dark energy emission from a de Sitter Universe

The evolution of a de Sitter Universe is the base for both the accelerated Universe and the late stationary Universe. So how do we differentiate between both universes? In this paper, we state that it is not possible to design an experiment using luminous or angular distances to distinguish between both cases because they are the same during the de Sitter phase. However, this equivalence allows us to predict a signal of it a constant dark energy emission with a signal peak around 29.5 MeV, in where according to our astrophysical test of survival probability, the radiation must be non-standard photons. Remarkably, experiments beyond EGRET and COMPTEL could observe an excess of gamma photons in this predicted region, coming from a possible decay process of the dark energy emission, which might constitute the possible smoking gun of a late stationary Universe with the continuous creation of non-standard radiation, an alternative approach to understand the current stages of the Universe evolution.

astro-ph.CO↗

arXiv2023

Constraining uber gravity with recent observations and studying the $H_0$ problem

This paper studies both $Λ$CDM and CDM models under the über gravity theory, named ü$Λ$CDM and üCDM respectively. We report bounds over their parameter phase-space using several cosmological data, in particular, the recent Pantheon+ sample. Based on the joint analysis, the best fit value of the über characteristic parameter is $z_\oplus = 0.046^{+0.047}_{-0.032}$ and $z_\oplus = 1.382^{+0.020}_{-0.021}$ at 68\% confidence level for ü$Λ$CDM and üCDM respectively. Although über gravity can successfully mimics the cosmological constant, we find that the $\mathbb{H}0(z)$ diagnostic suggests the $H_0$ tension is not alleviated. Finally, both models are statistically compared with $Λ$CDM through the Akaike and Bayesian information criteria. Both über gravity models and $Λ$CDM are equally preferred for most of the single samples, in particular, ü$Λ$CDM is not rejected by the CMB data. However, there is strong evidence against them for the joint analysis.

astro-ph.CO↗

arXiv2023

Cosmology under the fractional calculus approach: a possible $H_0$ tension resolution?

Recently, a new field of study called fractional cosmology has emerged. It uses fractional calculus to modify the standard derivative equations and change the Friedmann equations. The evolution of cosmic species densities is also affected by the $μ$ fractional parameter and the age of the Universe $t_0$. This new approach to cosmology modifies the Friedmann equations and allows for a late cosmic acceleration without the need for a dark energy component. This could be a breakthrough in solving longstanding problems in cosmology. By analyzing observational Hubble data and Type Ia supernovae, we have been able to place strict constraints on the fractional and cosmological parameters. Our results suggest that the Universe may be older than previously estimated. We also explore whether fractional cosmology can help resolve the $H_0$ tension.

gr-qc↗

arXiv2023

An exponential equation of state of dark energy in the light of 2018 CMB Planck data

The dynamics of the Universe is analyzed using an exponential function for the dark energy equation of state, known as Gong-Zhang parameterization. The phase space of the free parameters presented in the model is constrained using Cosmic Microwave Background radiation, Cosmic Chronometers, modulus distance from Hydrogen II Galaxies, Type Ia Supernovae and measurements from Baryon Acoustic Oscillations, together with a stronger bound from a Joint analysis. The cosmological model is confronted with $Λ$CDM, observing there is a strong evidence for $Λ$CDM in the Joint analysis although the exponential model is preferred when the data are separated. Based on the Joint analysis, a value of $ω_0 = -1.202^{+0.027}_{-0.026}$ is found for the characteristic parameter presented in the equation of state. Additionally, the cosmographic parameters at current times are reported, having $q_0 = -0.789^{+0.034}_{-0.036}$, $j_0=1.779^{+0.130}_{-0.119}$, and a transition deceleration-acceleration redshift $z_T = 0.644^{+0.011}_{-0.012}$. Furthermore, the age of the Universe is estimated as $t_U = 13.788^{+0.019}_{-0.019}$ Gyrs. Finally, we open a discussion if this model could alleviate the $H_0$ and $S_8$ tensions.

astro-ph.CO↗

arXiv2022

Cosmology under the fractional calculus approach

Fractional cosmology modifies the standard derivative to Caputo's fractional derivative of order $μ$, generating changes in General Relativity. Friedmann equations are modified, and the evolution of the species densities depends on $μ$ and the age of the Universe $t_U$. We estimate stringent constraints on $μ$ using cosmic chronometers, Type Ia supernovae, and joint analysis. We obtain $μ=2.839^{+0.117}_{-0.193}$ within the $1σ$ confidence level providing a non-standard cosmic acceleration at late times; consequently, the Universe would be older than the standard estimations. Additionally, we present a stability analysis for different $μ$ values. This analysis identifies a late-time attractor corresponding to a power-law decelerated solution for $μ< 2$. Moreover, a non-relativistic critical point exists for $μ> 1$ and a sink for $μ> 2$. This solution is a decelerated power-law if $1 < μ< 2$ and an accelerated power-law solution if $μ> 2$, consistent with the mean values obtained from the observational analysis. Therefore, for both flat FLRW and Bianchi I metrics, the modified Friedmann equations provide a late cosmic acceleration under this paradigm without introducing a dark energy component. This approach could be a new path to tackling unsolved cosmological problems.

gr-qc↗

arXiv2022

Noncommutative Quantum Cosmology for the FLRW model in Unimodular Gravity

It is well known that classical Unimodular Gravity (UG) is equivalent to General Relativity, but is not clear the equivalence at the quantum level. Here we exhibit, in the UG framework, the Quantum Cosmology (QC) for a Friedmann-Lemaitre-Robertson-Walker (FLRW) universe, considering an inflationary scenario and also introducing a deformation on the commutation relations for the minisuperspace variables (NCC).

gr-qc↗

arXiv2022

Observational constraints and dynamical analysis of Kaniadakis horizon-entropy cosmology

We study the scenario of Kanadiakis horizon entropy cosmology which arises from the application of the gravity-thermodynamics conjecture using the Kaniadakis modified entropy. The resulting modified Friedmann equations contain extra terms that constitute an effective dark energy sector. We use data from Cosmic chronometers, Supernova Type Ia, HII galaxies, Strong lensing systems, and Baryon acoustic oscillations observations and we apply a Bayesian Markov Chain Monte Carlo analysis to construct the likelihood contours for the model parameters. We find that the Kaniadakis parameter is constrained around 0, namely, around the value where the standard Bekenstein-Hawking is recovered. Concerning the normalized Hubble parameter, we find $h=0.708^{+0.012}_{-0.011}$, a result that is independently verified by applying the $\mathbf{\mathbb{H}}0(z)$ diagnostic and, thus, we conclude that the scenario at hand can alleviate the $H_0$ tension problem. Regarding the transition redshift, the reconstruction of the cosmographic parameters gives $z_T=0.715^{+0.042}_{-0.041}$. Furthermore, we apply the AICc, BIC and DIC information criteria and we find that in most datasets the scenario is statistical equivalent to $Λ$CDM one. Moreover, we examine the Big Bang Nucleosynthesis (BBN) and we show that the scenario satisfies the corresponding requirements. Additionally, we perform a phase-space analysis, and we show that the Universe past attractor is the matter-dominated epoch, while at late times the Universe results in the dark-energy-dominated solution. Finally, we show that Kanadiakis horizon entropy cosmology accepts heteroclinic sequences, but it cannot exhibit bounce and turnaround solutions.

astro-ph.CO↗

arXiv2022

Kaniadakis holographic dark energy: observational constraints and global dynamics

We investigate Kaniadakis-holographic dark energy by confronting it with observations. We perform a Markov Chain Monte Carlo analysis using cosmic chronometers, supernovae type Ia, and Baryon Acoustic Oscillations data. Concerning the Kaniadakis parameter, we find that it is constrained around zero, namely around the value in which Kaniadakis entropy recovers standard Bekenstein-Hawking one. Additionally, for the present matter density parameter $Ω_m^{(0)}$, we obtain a value slightly smaller compared to $Λ$CDM scenario. Furthermore, we reconstruct the evolution of the Hubble, deceleration and jerk parameters extracting the deceleration-acceleration transition redshift as $z_T = 0.86^{+0.21}_{-0.14}$. Finally, performing a detailed local and global dynamical system analysis, we find that the past attractor of the Universe is the matter-dominated solution, while the late-time stable solution is the dark-energy-dominated one.

astro-ph.CO↗