arXiv subjects

Gerardo Morales-Navarrete

Publications and source records attributed to Gerardo Morales-Navarrete.

4 recordsLinked to original sources

arXiv2026

Fullshape power spectrum for the Symmetron modified gravity model

We make use of the perturbation theory for modified gravity models that we developed in previous works and apply it to construct the fullshape galaxy power spectrum for the Symmetron modified gravity model. First, we study the growth rate, that is a scale dependent quantity, and compare our results with those of the $n=1 $ Hu-Sawcki (HS) model, finding that the Symmetron has a growth quite similar to the HS F6 in the wavenumber interval $0.01 \leq k \leq 0.1 $ and for redshifts where Symmetron model is viable. We also propose a growth parametrization that turns to be a good approximation for the HS and Symmetron models, with a deviation less than $0.6 \%$. To compute the RSD multipoles we employ an expansion of the velocity moments generating function that is suitable for general modified gravity models. Later, we apply the fk-Perturbation Theory (fkPT) approximation to reduce the computation time of nonlinear kernels, to find the fullshape galaxy power spectrum for the Symmetron, and study the differences with HS model. The RSD multipoles of the Symmetron result similar to those of the HS F6 model. Next, we integrate this theory to an MCMC sampler and validate our results by fitting our parameters to EZMocks to recover the parameters that bring the model to GR. We found a similar agreement in the model validation between Symmetron and F6 model, recovering the simulation cosmological parameters, and concluding that our pipeline is ready to make cosmological parameters' inference with real data.

astro-ph.CO↗

arXiv2026

Effects of Symmetron on growth and RSD multipoles

In this work, we investigate the effects of the growth rate scale dependence in the Symmetron modified gravity (MG) model on cosmic structure formation and we analyze the redshift-space distortion (RSD) multipoles, comparing with the Hu-Sawicki $f(R)$ model (specifically the F6) and the standard $Λ$CDM model. The analysis employs a scale-dependent growth equation and utilizes the fk-PT perturbation theory approach, implemented in the FOLPS-nu code, to compute the full 1-loop power spectrum multipoles, in particular, the monopole and quadrupole ($\ell=0,2$, respectively). The results show that at redshift $z=0$, the monopole of both MG models is suppressed compared to $Λ$CDM, with the Symmetron being closer to the standard model, while the quadrupole presents the opposite behavior. To validate the pipeline, we use General Relativity (GR) mock catalogs (EZMocks), since suitable Symmetron simulations are not available. The main result is that the Markov Chain Monte Carlo (MCMC) analysis successfully recovers the expected GR limit (i.e., $β_0 \approx 0$) from the Symmetron model when applied to this mock data, confirming the viability of our methodology for cosmological inference. Then, we conclude that the pipeline is prepared to test MG models against current and near-future galaxy surveys.

astro-ph.CO↗

arXiv2019

A thermodynamics revision of Rastall gravity

In this work we study some aspects of the Rastall gravity, being the thermodynamics consistency of the model the core of this paper, for this purpose we will consider the dynamical equations of Rastall model in a flat FLRW geometry. Under a holographic description can be seen that this scenario for gravity contributes to the energy density of the fluid with an extra term that can be related to the deceleration parameter, providing a way to estimate the value of the Rastall parameter, termed as $ξλ$, at present time. By adopting a specific Ansatz for the $ξλ$ term it is possible to determine that the behaviour of the Hubble parameter in Rastall gravity has a similar aspect to the $Λ$CDM model at late times, but at thermodynamics level differs from the standard cosmology since the adiabatic behaviour for the entropy depends on the value of the parameter state, $ω$. However, the entropy has a positive growth and simultaneously its convexity condition can be guaranteed; when other contributions are considered such as matter production and chemical potential, the adiabatic expansion can not be achieved, but the theory keeps its thermodynamics consistency. The chemical potential seems to have an interesting role since at effective level we could have a cosmological constant or phantom expansion in the model.

gr-qc↗

arXiv2019

Qualitative description of the universe in the interacting fluids scheme

In this work we present a qualitative description of the evolution of a curved universe when we consider the interacting scheme for the constituents of the dark sector. The resulting dynamics can be modeled by a set of Lotka-Volterra type equations. For this model a future singularity is allowed, therefore the cyclic behavior for the energy interchange between the components of the universe is present only at some stage of the cosmic evolution. Due to the presence of the future singularity, the model exhibits global instability.

gr-qc↗