arXiv subjects

Diogo H. F. de Souza

Publications and source records attributed to Diogo H. F. de Souza.

5 recordsLinked to original sources

arXiv2026

Modeling Redshift Uncertainties in Roman Weak Lensing Cosmology

Cosmological constraints using weak gravitational lensing measurements from the Roman Space Telescope will require a powerful method for modelling uncertainties in the galaxy redshift distribution. In this work, we use an optimized version of the principal component analysis (PCA) to model uncertainties in the full shape of the redshift distributions, a method proposed by \cite{pca_method} and recently used in the Dark Energy Survey Y6 analysis. Here, we implement this new approach within the Roman High Latitude Imaging Survey (HLIS) Cosmology Project Infrastructure Team (PIT) pipeline, namely Cobaya-Cosmolike Joint Architecture (\texttt{CoCoA}). To validate the PCA in mitigating biases on cosmological parameters, $S_8$ and $Ω_m$, we use a set of redshift distributions from \texttt{Cardinal} generated for a variety of Roman configurations. Overall, when the simulated cosmic shear data vector is not strongly miscalibrated relative to the fiducial one, both the mean-shift and the PCA-based approaches produce consistent cosmological constraints when marginalizing over nuisance parameters. For mild to strong miscalibration, including additional PCs progressively mitigates biases in $S_8$ and $Ω_m$, and can achieve comparable performance with fewer parameters than the nine tomographic-bin mean-shift model.

astro-ph.CO↗

arXiv2026

Late-Transition Interacting Thawer Dark Energy: Model Definition and Benchmark Consistency Tests

We formulate the late-transition interacting thawer (LTIT) as a late-activating, variable-coupling realization of coupled quintessence in which a canonical scalar field couples conformally only to cold dark matter. The construction is a non-universal dark-sector interaction: baryons and radiation remain minimally coupled, while CDM follows a conformally related metric. This structure ties three observational sectors to one microscopic mechanism--the pre-recombination calibration scale, the low-redshift expansion history, and the coupled growth response. We derive the exact background equations, the exact CDM scaling identity $\rhoc(a)=ρ_{c0}a^{-3}C[ϕ(a)]/C(ϕ_0)$, and the coupled CDM--scalar perturbation equations in synchronous gauge in a form suitable for Einstein--Boltzmann solvers. In the representative benchmarks, $Ω_ϕ(z_*)\sim10^{-9}$, $|Δr_d/r_d|\le3.82\times10^{-3}$, and $\max_{0<z<3}|E/E_{Λ\mathrm{CDM}}-1|\le0.380\%$, while the quasi-static growth indicator ranges from $0.725\%$ to $5.94\%$. LTIT therefore demonstrates how late activation can preserve the early calibration sector while producing a perturbation-sensitive signature, providing a concrete target for Boltzmann-level tests of interacting dark energy.

gr-qc↗

arXiv2025

Investigating Late-Time Dark Energy and Massive Neutrinos in Light of DESI Y1 BAO

Baryonic Acoustic Oscillation (BAO) data from the Dark Energy Spectroscopic Instrument (DESI), in combination with Cosmic Microwave Background (CMB) data and Type Ia Supernovae (SN) luminosity distances, suggests a dynamical evolution of the dark energy equation of state with a phantom phase ($w < -1$) in the past when the so-called $w_0w_a$ parametrization $w(a) = w_0 + w_a(1-a)$ is assumed. In this work, we investigate more general dark energy models that also allow a phantom equation of state. We consider three cases: an equation of state with a transition feature, a model-agnostic equation of state with constant values in chosen redshift bins, and a k-essence model. Since the dark energy equation of state is correlated with neutrino masses, we reassess constraints on the neutrino mass sum focusing on the model-agnostic equation of state. We find that the combination of DESI BAO with Planck 2018 CMB data and SN data from Pantheon, Pantheon+, or Union3 is consistent with an oscillatory dark energy equation of state, while a monotonic behavior is preferred by the DESY5 SN data. Performing model comparison techniques, we find that the $w_0w_a$ parametrization remains the simplest dark energy model that can provide a better fit to DESI BAO, CMB, and all SN datasets than $Λ$CDM. Constraints on the neutrino mass sum assuming dynamical dark energy are relaxed compared to $Λ$CDM and we show that these constraints are tighter in the model-agnostic case relative to $w_0w_a$ model by $70\%-90\%$.

astro-ph.CO↗

arXiv2024

Early dark energy constraints with late-time expansion marginalization

Early dark energy (EDE) is an extension to the $Λ$CDM model, proposed to reduce the tension between the measurements of the Hubble constant $H_0$ from the cosmic microwave background (CMB) and from the local cosmic distance ladder. However, this model increases the $S_8$ tension between CMB and large scale structure measurements. Analyses of galaxy clustering and lensing correlation functions report a decreased preference for EDE and its effect on the Hubble tension. Smooth dark energy models affect growth of structure through the background expansion. In this work, we study the inclusion of a general, smooth late-time dark energy modification in combination with EDE and obtain constraints on EDE marginalized over the late-time expansion. We assess the impact on the $S_8$ and Hubble tensions. In order to generalize the late expansion, we use a late dark energy fluid model with a piecewise constant equation of state $w(z)$ over 3, 5 and 10 redshift bins in the window $z \in [0,3]$. We show that, when analyzing ACT and Planck CMB data combined with Pantheon supernovae, BAO from 6dF, SDSS and BOSS, Planck 2018 CMB lensing and Dark Energy Survey cosmic shear and clustering data, the inclusion of a general smooth dark energy modification at late times has no significant effect on $S_8$ and EDE parameter constraints. Using the aforementioned datasets, the EDE fraction constraint with late-time expansion marginalization is $f_\mathrm{EDE} = 0.067^{+0.019}_{-0.027}$ using 3 redshift bins, with similar results for 5 and 10 redshift bins. This work shows that in order to solve simultaneously the Hubble and $S_8$ tensions, one needs a mechanism for increasing the clustering of matter at late times different from a simple change in the background evolution of late dark energy. [Abridged]

astro-ph.CO↗

arXiv2023

Can neutrino-assisted early dark energy models ameliorate the $H_0$ tension in a natural way?

The idea of neutrino-assisted early dark energy ($ν$EDE), where a coupling between neutrinos and the scalar field that models early dark energy (EDE) is considered, was introduced with the aim of reducing some of the fine-tuning and coincidence problems that appear in usual EDE models. In order to be relevant in ameliorating the $H_0$ tension, the contribution of EDE to the total energy density ($f_\text{EDE}$) should be around 10\% near the redshift of matter-radiation equality. We verify under which conditions $ν$EDE models can fulfill these requirements for a model with a quartic self-coupling of the EDE field and an exponential coupling to neutrinos. We find that in the situation where the EDE field is frozen initially, the contribution to $f_\text{EDE}$ can be significant but it is not sensitive to the neutrino-EDE coupling and does not address the EDE coincidence problem. On the other hand, if the EDE field starts already dynamical at the minimum of the effective potential, it tracks this time-dependent minimum that presents a feature triggered by the neutrino transition from relativistic to nonrelativistic particles. This feature generates $f_\text{EDE}$ in a natural way at around this transition epoch, that roughly coincides with the matter-radiation equality redshift. For the set of parameters that we considered we did not find values that satisfy the requirements on the background cosmological evolution to mitigate the Hubble tension in a natural way in this particular $ν$EDE model.

astro-ph.CO↗