arXiv subjects

Daniela Narbona

Publications and source records attributed to Daniela Narbona.

3 recordsLinked to original sources

arXiv2024

Scalar probes on wormholes in Lovelock theories with unique vacuum

In this paper we present a new family of wormhole geometries in Lovelock theories with a unique vacuum, and study their stability under scalar field perturbations. As the solutions already known in the literature for Chern-Simons gravity on AdS, the new wormholes are characterized by a single integration constant $ρ_{0}$, that parameterizes the contribution to the mass coming from each boundary, which cancel each other, leading to a new example of "mass without mass". The stability of these new configurations, as well as other previously constructed in the literature is explored under scalar field perturbations. The stability is ensured provided the mass of the scalar perturbation is above a deformed Breitenlohner-Freedman bound which is sensitive to the value of $ρ_{0}$.

hep-th↗

arXiv2018

Non-minimally coupled scalar field cosmology with torsion

In this work we present a generalized Brans-Dicke lagrangian including a non-minimally coupled Gauss-Bonnet term without imposing the vanishing torsion condition. In the resulting field equations, the torsion is closely related to the dynamics of the scalar field, i.e., if non-minimally coupled terms are present in the theory, then the torsion must be present. For the studied lagrangian we analyze the cosmological consequences of an effective torsional fluid and we show that this fluid can be responsible for the current acceleration of the universe. Finally, we perform a detailed dynamical system analysis to describe the qualitative features of the model, we find that accelerated stages are a generic feature of this scenario.

gr-qc↗

arXiv2017

Nonminimal couplings, gravitational waves, and torsion in Horndeski's theory

The Horndeski Lagrangian brings together all possible interactions between gravity and a scalar field that yield second-order field equations in four-dimensional spacetime. As originally proposed, it only addresses phenomenology without torsion, which is a non-Riemannian feature of geometry. Since torsion can potentially affect interesting phenomena such as gravitational waves and early Universe inflation, in this paper we allow torsion to exist and propagate within the Horndeski framework. To achieve this goal, we cast the Horndeski Lagrangian in Cartan's first-order formalism, and introduce wave operators designed to act covariantly on p-form fields that carry Lorentz indices. We find that nonminimal couplings and second-order derivatives of the scalar field in the Lagrangian are indeed generic sources of torsion. Metric perturbations couple to the background torsion and new torsional modes appear. These may be detected via gravitational waves but not through Yang-Mills gauge bosons.

gr-qc↗