arXiv subjects

Marcela Campista

Publications and source records attributed to Marcela Campista.

4 recordsLinked to original sources

arXiv2024

Cosmological constraints on $R^2$-corrected Appleby-Battye model

Nowadays, efforts are being devoted to the study of alternative cosmological scenarios in which modifications of General Relativity have been proposed to explain the late cosmic acceleration without assuming the existence of dark energy. In this scenario, we investigate the $R^2$-AB model, which consists of an $f(R)$ model with only one extra free parameter, $b$, in addition to the 6 of the flat-$Λ$CDM. Regarding this model, it was already shown that a positive value for $b$ is required for the model to be consistent with Solar System tests, moreover, the condition for the existence of a de~Sitter state requires $b \ge 1.6$. To impose observational constraints on the $R^2$-AB model we consider three datasets: 31 $H(z)$ measurements from Cosmic Chronometers (CC), 20 $[{fσ}_{8}](z)$ measurements from Redshift-Space Distortion (RSD), and the most recent type Ia Supernovae (SNe Ia) sample from Pantheon+. Next, we perform two different analyses: we have considered only SNe Ia data and the combined likelihood SNe+CC+RSD. The first one has provided $b=2.28^{+6.52}_{-0.55}$, while the second one $b=2.18^{+5.41}_{-0.55}$. In the first case it was necessary to set the absolute magnitude $M_B = -19.253$ from SH0ES collaboration, while in the second we did a marginalization over the Hubble constant $H_0$ in the normalized growth function. We have also observed that the $H_0-M_B$ degeneracy was broken by adding CC data to the SNe data. Additionally, we perform illustrative analyses that compare this $f(R)$ model with the flat-$Λ$CDM model, considering several values of the parameter $b$, for diverse cosmological functions like the Hubble function $H(z)$, the equation of state $w_{\rm eff}(z)$, the parametrized growth rate of cosmic structures $[fσ_8](z)$, and $σ_8(z)$. We conclude that the model fits well the data, but the parameter $b$ was not unambiguously constrained.

astro-ph.CO↗

arXiv2022

Observational constraints on Starobinsky $f(R)$ cosmology from cosmic expansion and structure growth data

The unknown physical nature of the Dark Energy motivates in cosmology the study of modifications of the gravity theory at large distances. One of these types of modifications is to consider gravity theories, generally termed as $f(R)$. In this paper we use observational data to both constrain and test the Starobinsky $f(R)$ model \cite{Starobinsky2007}, using updated measurements from the dynamics of the expansion of the universe, $H(z)$; and the growth rate of cosmic structures, $[fσ_8](z)$, where the distinction between the concordance $Λ$CDM model and modified gravity models $f(R)$ becomes clearer. We use MCMC likelihood analyses to explore the parameters space of the $f(R)$ model using $H(z)$ and $[fσ_8](z)$ data, both individually and jointly, and further, examine which of the models best fits the joint data. To further test the Starobinsky model, we use a method proposed by Linder \cite{Linder2017}, where the data from the observables is jointly binned in redshift space. This allows to further explore the model's parameter that better fits the data in comparison to the $Λ$CDM model. The joint analysis of $H(z)$ and $[fσ_8](z)$ show that the $n=2$--Starobinsky $f(R)$ model fits well the observational data. In the end, we confirm that this joint analysis is able to break the degenerescence between modified gravity models as proposed in the original work \cite{Starobinsky2007}. Our results indicate that the $f(R)$ Starobinsky model provides a good fit to the currently available data for a set of values of its parameters, being, therefore, a possible alternative to the $Λ$CDM model.

astro-ph.CO↗

arXiv2020

Probing the Seesaw Mechanism with Cosmological Data

We investigate cosmological consequences of an inflationary model which incorporates a generic seesaw extension (types I and II) of the Standard Model of Particle Physics. A non-minimal coupling between the inflaton field and the Ricci scalar is considered as well as radiative corrections at one loop order. This connection between the inflationary dynamics with neutrino physics results in a predictive model whose observational viability is investigated in light of the current cosmic microwave background data, baryon acoustic oscillation observations and type Ia supernovae measurements. Our results show that the non-minimal coupled seesaw potential provides a good description of the observational data when radiative corrections are positive. Such result favours the type II seesaw mechanism over type I and may be an indication for physics beyond the Standard Model.

astro-ph.CO↗

arXiv2017

Testing non-minimally coupled inflation with CMB data: a Bayesian analysis

We use the most recent cosmic microwave background (CMB) data to perform a Bayesian statistical analysis and discuss the observational viability of inflationary models with a non-minimal coupling,~$ξ$, between the inflaton field and the Ricci scalar. We particularize our analysis to two examples of small and large field inflationary models, namely, the Coleman-Weinberg and the chaotic quartic potentials. We find that (i) the $ξ$ parameter is closely correlated with the primordial amplitude; (ii) although improving the agreement with the CMB data in the $r - n_s$ plane, where $r$ is the tensor-to-scalar ratio and $n_s$ the primordial spectral index, a non-null coupling is strongly disfavoured with respect to the minimally coupled standard $Λ$CDM model, since the upper bounds of the Bayes factor (odds) for $ξ$ parameter are greater than $150:1$.

astro-ph.CO↗