arXiv subjects

S. Santos da Costa

Publications and source records attributed to S. Santos da Costa.

7 recordsLinked to original sources

arXiv2025

Forecasting constraints on quintessential inflation from future generation of galaxy and CMB surveys

We investigate the constraining power of future CMB and galaxy surveys on models of quintessential inflation realized within the framework of $α$-attractors. We analyze how these future datasets will probe the parameter space of $α$-attractor quintessential inflation, specifically the inflationary potential parameters. Our results demonstrate that the synergy between CMB-S4, LiteBIRD, and Euclid can significantly tighten the bounds on the model parameters, achieving forecasted $1σ$ uncertainties of $α=2\pm 0.17$, $n_s=0.965\pm 0.0014$, $\ln(10^{10}A_s)=3.0447\pm 0.0029$ for the CMB+GC$_{sp}$ case. This level of sensitivity will enable us to discriminate between different realizations of quintessential inflation and test the attractor behavior characteristic of these models.

astro-ph.CO↗

arXiv2025

Cuscuton-like contribution to dark energy evolution

This work deals with the presence of the cuscuton term in the otherwise standard dark energy evolution under the usual FLRW background. We disclose a first-order framework similar to the Hamilton-Jacobi formalism, which helps us to solve the equations of motion and find analytical solutions. We explore several possibilities, concentrating mainly on how the cuscuton-like contribution works to modify cosmic evolution. Some results are of current interest since they describe scenarios capable of changing the evolution, adding or excluding possible distinct phases during the Universe's expansion history. Additionally, we present interesting constraints on the cuscuton-like contribution for the dark energy evolution using a set of homogeneous geometrical observational probes. Finally, based on the Akaike Information Criterion (AIC), we perform a statistical comparison of the cuscuton-like model with $Λ$CDM, and find strong support for our model.

astro-ph.CO↗

arXiv2023

Cosmological models in $f(R,T)$-$Λ(ϕ)$ gravity

The Universe is currently in a phase of accelerated expansion, a fact that was experimentally proven in the late 1990s. Cosmological models involving scalar fields allow the description of this accelerated expansion regime in the Cosmos and present themselves as a promising alternative in the study of the inflationary eras, especially the actual one which is driven by the dark energy. In this work we use the $f(R, T) - Λ(ϕ)$ gravity to find different cosmological scenarios for our Universe. We also introduce a new path to derive analytic cosmological models which may have a non-trivial mapping between $f$ and $T$. We show that the analytic cosmological models obtained with this approach are compatible with a good description of the radiation era. In addition, we investigated the inflationary scenario and obtained a good agreement for the scalar spectral index $n_s$. Concerning the tensor-to-scalar ratio $r$, we found promising scenarios compatible with current CMB data.

gr-qc↗

arXiv2022

Warm $β$-exponential inflation and the Swampland Conjectures

We investigate theoretical and observational aspects of a warm inflation scenario driven by the $β$-exponential potential, which generalizes the well-known power law inflation. In such a scenario, the decay of the inflaton field into radiation happens during the inflationary phase. In our study, we consider a dissipation coefficient ($Γ$) with cubic dependence on the temperature ($T$) and investigate the consequences in the inflationary dynamics, focusing on the impact on the spectral index $n_s$, its running $n_{run}$ and tensor-to-scalar ratio $r$. We find it possible to realize inflation in agreement with current cosmic microwave background data in weak and strong dissipation regimes. We also investigate theoretical aspects of the model in light of the swampland conjectures, as warm inflation in the strong dissipation regime has been known as a way to satisfy the three conditions currently discussed in the literature. We find that when $Γ\propto T^3$, the $β$-exponential model can be accommodated into the conjectures.

astro-ph.CO↗

arXiv2022

Brane inflation driven by an arctan potential: CMB constraints and Reheating

We investigate the early universe evolution in the context of brane inflation driven by a supergravity-inspired $\arctan$ potential. We performed a slow-roll and a semi-analytical reheating analyses and obtained constraints on the inflationary parameters in agreement with Planck 2018 data. We also employed a Markov Chain Monte Carlo analysis to perform a parameter estimation of the cosmological parameters, obtaining results in good agreement with the currently available cosmic microwave background and baryon acoustic oscillation data. This work establishes the general theoretical predictions of the $\arctan$ model, with the results of the statistical analysis corroborating its observational viability.

hep-th↗

arXiv2021

Observational constraints on $α$-attractor inflationary models with a Higgs-like potential

We investigate the observational viability of a class of $α$-attractors inflationary models in light of the most recent Cosmic Microwave Background (CMB) and Large-Scale Structure (LSS) data. By considering a double-well potential we perform a slow-roll analysis to study the behavior of this class of models, which is a continuous interpolation between the chaotic inflation for large values of $α$ and the universal attractor, i.e., $n_s=1- 2/N$ and $r=α12/N^2$ for small $α$, where $n_s$ is the scalar spectral index, $r$ is the tensor-to-scalar ratio, and $N$ is the e-fold number. In order to explore the parameter space of the model, we also perform a MCMC analysis and find $α=7.56\pm 5.15$ ($1σ$).

astro-ph.CO↗

arXiv2021

Brane inflation and the robustness of the Starobinsky inflationary model

The first inflationary model conceived was the one proposed by Starobinsky which includes an additional term quadratic in the Ricci-scalar R in the Einstein-Hilbert action. The model is now considered a target for several future cosmic microwave background experiments given its compatibility with current observational data. In this paper, we analyse the robustness of the Starobinsky inflation by inserting it into a generalized scenario based on a $β$-Starobinsky inflation potential, which is motivated through brane inflation. In the Einstein frame, the generalized model recovers the original model for $β=0$, whereas $\forall β\neq 0$ represents an extended class of models that admit a wider range of solutions. We investigate limits on $β$ from current cosmic microwave background and baryonic acoustic oscillation data and find that only a small deviation from the original scenario is allowed, $β=-0.08 \pm 0.12$ (68% C.L.), which is fully compatible with zero and confirms the robustness of the Starobinsky inflationary model in light of current observations.

astro-ph.CO↗