arXiv subjects

Vitor da Fonseca

Publications and source records attributed to Vitor da Fonseca.

9 recordsLinked to original sources

arXiv2026

Mass-Varying Neutrinos from an Inverse Symmetron

Neutrinos enter cosmology in different ways and are constrained by distinct observational probes across different epochs: as a relativistic species at high redshift, as a massive but clustering-suppressing component at low redshift, and as a particle physics observable in laboratory experiments. Low (verging on negative) bounds on neutrino mass from galaxy surveys motivate exploration of models where neutrinos may couple to dark energy, causing their mass to vary over cosmic evolution. If the coupling involves an inverse phase transition (symmetry broken, rather than restored, as neutrinos become nonrelativistic) this can tame instabilities in neutrino growth, appear as a lower neutrino mass in galaxy surveys, and add extra suppression to the matter power spectrum. We find that the late-time decoupling shuts down the fifth force and inhibits the excessive growth of neutrino perturbations, thereby eliminating linear-regime instabilities. The model may potentially address the Hubble tension via an early dark energy component localized around the time of recombination.

astro-ph.CO↗

arXiv2026

Scaling solutions in three-form cosmology

A hybrid three-form model of dark energy is developed in order to identify scaling solutions, a long-sought feature in three-form cosmology. Exploiting Hodge dualities, the theory is formulated in terms of two scalar functions that are associated with the conjugate momentum, and the three-form dual vector in an isotropic background. The resulting Lagrangian yields a stable scaling attractor where the three-form energy density tracks the dominant background fluid. A dynamical mechanism is also identified that naturally drives the system out of this regime toward a late-time accelerated phase distinguishable from a cosmological constant. This constitutes the first realization of scaling behavior within a three-form dark energy framework.

astro-ph.CO↗

arXiv2024

Non-canonical 3-form dark energy

In this study, we meticulously construct a 3-form Lagrangian designed to mimic the dynamics of both dust matter in the past and dark energy driving the acceleration in the present era. A dynamical systems approach is used to investigate the underlying behavior of the cosmological background. By investigating the influence of the potential slope and initial conditions on the dynamical solutions, we identify distinct viable scenarios capable of replicating a De Sitter universe in the present epoch. An intriguing aspect of the model is the existence of solutions describing multiple inflationary phases in which the 3-form self-interacting potential decays rapidly.

gr-qc↗

arXiv2024

Relaxing cosmological constraints on current neutrino masses

We show that a mass-varying neutrino model driven by scalar field dark energy relaxes the existing upper bound on the current neutrino mass to ${\sum m_ν< 0.72}$ eV. We extend the standard $Λ$ cold dark matter model by introducing two parameters: the rate of change of the scalar field with the number of $e$-folds and the coupling between neutrinos and the field. We investigate how they affect the matter power spectrum, the cosmic microwave background anisotropies and its lensing potential. The model is tested against Planck observations of temperature, polarization, and lensing, combined with baryon acoustic oscillation measurements that constrain the background evolution. The results indicate that small couplings favor a cosmological constant, while larger couplings favor a dynamical dark energy, weakening the upper bound on current neutrino masses.

astro-ph.CO↗

arXiv2023

Coupling quintessence kinetics to electromagnetism

We propose a general model where quintessence couples to electromagnetism via its kinetic term. This novelty generalizes the linear dependence of the gauge kinetic function on $ϕ$, commonly adopted in the literature. The interaction naturally induces a time variation of the fine-structure constant that can be formulated within a disformally coupled framework, akin to a Gordon metric. Through a suitable parametrization of the scalar field and the coupling function, we test the model against observations sensitive to the variation of $α$. We undertake a Bayesian analysis to infer the free parameters with data from Earth based, astrophysical and early Universe experiments. We find that the evolution of $α$ is specific to each cosmological era and slows down at late times when dark energy accelerates the Universe. While the most stringent bound on the interaction is obtained from atomic clocks measurements, the quasars provide a constraint consistent with weak equivalence principle tests. This promising model is to be further tested with upcoming and more precise astrophysical measurements, such as those of the ESPRESSO spectrograph.

astro-ph.CO↗

arXiv2023

Is there evidence for CIDER in the Universe?

In this work we analyze the full linear behaviour of the constrained interacting dark energy (CIDER) model, which is a conformally coupled quintessence model tailored to mimic a $Λ$CDM expansion. We compute the matter and temperature anisotropies power spectra and test the model against recent observational data. We shed light on some particular subtleties of the background behaviour that were not fully captured in previous works, and study the physics of the linear cosmological observables. One novelty found was that matter perturbations are enhanced at large scales when compared with the ones of the standard $Λ$CDM. The reason and impact of this trend on the cosmological observables and on the physics of the early Universe are considered. We find that the introduction of the coupling parameter alleviates the $σ_8$ tension between early and late time probes although Planck data favours the $Λ$CDM limit of the model.

astro-ph.CO↗

arXiv2022

Fundamental Physics with ESPRESSO, Constraining a simple parametrisation for varying $α$

The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant, $α$, through measurements along the line of sight of a bright quasar with a precision of $1.36$ ppm at $1σ$ level. This imposes new constraints on cosmological models with a varying $α$. We assume such a model where the electromagnetic sector is coupled to a scalar field dark energy responsible for the current acceleration of the Universe. We parametrise the variation of $α$ with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field. The objective of this work is to constrain these parameters with both astrophysical and local probes. We also carried out a comparative analysis of how each data probe may constrain our parametrisation. We performed a Bayesian analysis by comparing the predictions of the model with observations. The astrophysical datasets are composed of quasar spectra measurements, including the latest ESPRESSO data point, as well as Planck observations of the cosmic microwave background. We combined these with local results from atomic clocks and the MICROSCOPE experiment. The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a $Λ$CDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the Eötvös parameter local bound. More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of $α$ as it probes an interval of redshift not accessible to other types of observations. However, for this particular model, current available data favour a null variation of $α$ resulting mostly from the strong MICROSCOPE limits.

astro-ph.CO↗

arXiv2022

Simple parametrisation for coupled dark energy

We propose a phenomenological generalisation of the standard model with only one extra degree of freedom that parametrises the evolution of a scalar field responsible for the cosmic acceleration. The model also foresees an additional parameter in the form of a coupling between dark energy and dark matter. This model captures a large diversity of dark energy evolutions at low redshift and could usefully complement common CPL parametrisations widely used. In this context, we have been constraining the parametrisation with data from Planck and KiDS, bringing different results between the early and late universe observations.

astro-ph.CO↗

arXiv2021

A simple parametrisation for coupled dark energy

As an alternative to the popular parametrisations of the dark energy equation of state, we construct a quintessence model where the scalar field has a linear dependence on the number of e-folds. Constraints on more complex models are typically limited by the degeneracies that increase with the number of parameters. The proposed parametrisation conveniently constrains the evolution of the dark energy equation of state as it allows for a wide variety of time evolutions. We also consider a non-minimal coupling to cold dark matter. We fit the model with Planck and KiDS observational data. The CMB favours a non-vanishing coupling with energy transfer from dark energy to dark matter. Conversely, gravitational weak lensing measurements slightly favour energy transfer from dark matter to dark energy, with a substantial departure of the dark energy equation of state from -1.

astro-ph.CO↗