arXiv subjects

Jose Perdiguero

Publications and source records attributed to Jose Perdiguero.

6 recordsLinked to original sources

arXiv2026

Gravitational Wave Birefringence in generalized Palatini Chern Simons

The cosmological propagation of gravitational waves (GWs) can exhibit amplitude and phase polarization distortions when parity symmetry is broken, a phenomenon known as cosmological birefringence. In this paper, we investigate the phenomenology of GW birefringence in a gravitational model $f(R)$ coupled to a dynamical Chern-Simons (dCS) term, analyzed in the metric and Palatini formalisms. At the background level, this model can lead to dynamical dark energy, while for GW propagation we find that the Palatini formalism predicts both amplitude and velocity birefringence, whereas the metric formalism predicts amplitude birefringence only. We also find that the birefringence effects can either be suppressed or enhanced by the $f(R)$ interactions, depending on the specific form of $f(R)$. Considering three common $f(R)$ models (Hu-Sawicki, Exponential, and Hyperbolic gravity) fit to recent cosmological data, we find that birefringence is enhanced relative to the $f(R) = R$ case, by $1-10\%$ in the Palatini formalism and up to a factor of 2 in the metric formalism. We also translate current GW birefringence constraints to bounds on the dCS coupling within our model. Finally, we show that in our model the birefringence effect grows polynomially with source redshift, in contrast to the linear-distance scaling commonly assumed in phenomenological models of GW birefringence in the current literature.

gr-qc↗

arXiv2024

A polynomial affine model of gravity: after ten years

The polynomial affine model of gravity was proposed as an alternative to metric and metric-affine gravitational models. What at the beginning was thought as a source of unpredictability, the presence of many terms in the action, turned out to be a milestone, since it contains all possible combinations of the fields compatible with the covariance under diffeomorphisms. Here, we present a review of the advances in the analysis of the model after ten years of its proposal, and sketch the guideline of our future perspectives.

gr-qc↗

arXiv2023

Inflationary scenarios in an effective polynomial affine model of gravity

In this paper we inquire inflationary scenarios built on a simplified version of the polynomial affine model of gravity. Given the absence of a metric tensor in the formulation of the model, we build a \emph{kinetic term} contracting the derivatives of scalar field with the most general $(2,0)$-tensor density build using the affine connection, and introduce a self-interacting potential via a scaling of the volume form. We analyse the cosmological solutions derived from this setup.

gr-qc↗

arXiv2023

Does the metric play a fundamental role in the building of gravitational models?

The idea that General Relativity could be an effective model, of a yet unknown theory of gravity, has gained momentum among theoretical physicists. The polynomial affine model of gravity is an alternative model of affine gravity that possesses many desirable features to pursue a quantum theory of gravitation. In this paper we argue that such features are a consequence of the lack of a metric structure in the building of the model, even though a emergent metric could be defined. The model introduces additional degrees of freedom associated to the geometric properties of the space, which might shed light to understand the nature of the dark sector of the Universe. When the model is coupled to a scalar field, it is possible to define inflationary scenarios.

gr-qc↗

arXiv2022

Polynomial affine model of gravity in three-dimensions

In this work, we explore a three-dimensional formulation of the polynomial affine model of gravity, which is a model that extends general relativity by relaxing the equivalence principle through the exclusion of the metric from the set of fundamental fields. In particular, in an attempt to gain insight of the role of the torsion and nonmetricity in the gravitational models, we consider homogeneous and isotropic cosmological models, for which their solutions are classified in a \emph{decisions tree}. We also show a few of these explicit solutions that allow the definition of (alternative/emergent) metrics derived from the connection.

gr-qc↗

arXiv2019

Emergent metric and geodesic analysis in cosmological solutions of (torsion-free) Polynomial Affine Gravity

Starting from an affinely connected space, we consider a model of gravity whose fundamental field is the connection. We build up the action using as sole premise the invariance under diffeomorphisms, and study the consequences of a cosmological ansatz for the affine connection in the torsion-free sector. Although the model is built without requiring a metric, we show that the nondegenerated Ricci curvature of the affine connection can be interpreted as an \emph{emergent} metric on the manifold. We show that there exists a parametrization in which the $(r,φ)$-restriction of the geodesics coincides with that of the Friedman--Robertson--Walker model. Additionally, for connections with nondegenerated Ricci we are able to distinguish between space-, time- and null-like self-parallel curves, providing a way to differentiate \emph{trajectories} of massive and massless particles.

gr-qc↗