arXiv subjects

Luiz Carlos Garcia de Andrade

Publications and source records attributed to Luiz Carlos Garcia de Andrade.

4 recordsLinked to original sources

arXiv2026

Action-level characterization of gravitational-wave propagation in dynamical Barbero--Immirzi gravity

We investigate which operators in first-order dynamical Barbero--Immirzi (BI) gravity control cosmological tensor propagation at the action level. Within a bosonic, two-derivative, curvature-linear Einstein--Cartan class, eliminating the algebraic Lorentz connection reveals a separation between the scalar sector and the tensor kinetic normalization. In particular, the Holst-to-Palatini ratio determines the scalar kinetic structure, whereas the transverse-traceless tensor mode is normalized by the parity-even Hilbert--Palatini coefficient. As a consequence, a minimal dynamical Holst sector with fixed parity-even normalization remains exactly on the general-relativistic tensor-propagation surface and does not generate anomalous gravitational-wave friction. We then construct a regular nonminimal parity-even realization in which the tensor normalization evolves cosmologically, derive the corresponding standard-siren observable, and apply current GWTC-3, GWTC-4.0, and GWTC-5.0 information as an observational test of this action-level tensor sector. The resulting constraints should therefore be interpreted as limits on the evolution of the tensor kinetic normalization rather than direct constraints on minimal BI torsion dynamics.

gr-qc↗

arXiv2026

Dynamical Barbero--Immirzi field coupled to quintessence: gravitational-wave propagation constraints and next-generation forecasts

We investigate the imprints of a dynamical Barbero--Immirzi (BI) field $γ(x)$ coupled to a quintessence scalar field $ϕ$ on gravitational-wave (GW) propagation. In the framework of Einstein--Cartan--Holst gravity, promoting $γ$ to a dynamical scalar introduces a stress--energy that back-reacts on the metric, modifying the GW friction term. A minimal coupling $\proptoβ\,ϕ^2γ^2$ between the BI field and quintessence leads to a two-parameter extension of the Belgacem--Maggiore parametrization, characterized by $\xBI$ (from the isolated BI field) and $\xcp$ (from the coupling). Using the LIGO--Virgo--KAGRA GWTC-3 dark-siren constraint $Ξ_0=1.2^{+0.7}_{-0.7}$, we obtain the first simultaneous constraints: $|\xBI|\lesssim0.7$ and $|\xcp|\lesssim0.13$ at 90\% credibility. We then forecast the sensitivity of next-generation detectors Einstein Telescope (ET) and Cosmic Explorer (CE), showing that a 10-year observation campaign can improve these bounds by roughly one to two orders of magnitude depending on the parameter---a factor of $\sim\!20$ for $\xBI$ and $\sim\!20$ for $\xcp$---reaching $σ(\xBI)\sim3\times10^{-2}$ and $σ(\xcp)\sim1.2\times10^{-2}$. Translated into microscopic parameters, this corresponds to $γ_{\rm dyn}\lesssim10^{-12}$ and $β\lesssim10^{-3}$, providing a powerful new observational window into the interplay between quantum-gravity phenomenology and dark energy.

gr-qc↗

arXiv2013

Stringent magnetic field limits from early universe dynamos cosmology with torsion

Earlier Bamba et al [JCAP (2012)] have obtained cosmological magnetic fields in teleparallel torsion theories of gravity that are not compatible with galactic dynamos. This result agrees with previous ones obtained by the author which shows [Phys Lett B (2012)] that anti-dynamo generalised theorem to torsion theories forbides such kind of dynamos to explain galactic magnetic fields of the order of $μ$G. More recently the author has suggested [IJAA (2012)] that a sort of Biermann battery could be obtained in torsioned cosmology. Nevertheless in this paper we show that this can be a particular result, since the second author did not took into account mean field dynamo equations in torsion field background. Actually it is shown that amplification or not of the magnetic field depends upon handness sign of the torsion field vector. It is shown that density fluctuations of spin-torsion density implies also a possibility of amplification of the cosmic magnetic fields. From WMAP data it is possible to estimate the spin-torsion fluctuation as $10^{-6}$ which represents an order of magnitude lower than the matter density. By making use of the gravitational couling of type $RF^{2}$ one obtains $10^{37}G$ for the Planck era magnetic field, which is a much more stringent limit than the ones obtained earlier. The magnetic field obtained today is $10^{-23}G$ is obtained which is able to seed galactic dynamos.

astro-ph.CO↗

arXiv2007

Twist, writhe and energy from the helicity of magnetic perturbed vortex filaments

The twist and writhe numbers and magnetic energy of an orthogonally perturbed vortex filaments are obtained from the computation of the magnetic helicity of geodesic and abnormal magnetohydrodynamical (MHD) vortex filament solutions. Twist is computed from a formula recently derived by Berger and Prior [J. Phys. A 39 (2006) 8321] and finally writhe is computed from the theorem that the helicity is proportional to the sum of twist and writhe. The writhe number is proportional to the total torsion and to integrals of the vector potential. The magnetic energy is computed in terms of the integral of the torsion squared which allows us to place a bound to energy in in the case of helical filaments due to a theorem by Fukumoto [J. Phys. Soc. Japan,(1987)] in fluid vortex filaments. It is also shown that filament torsion coincides with the magnetic twist in the case under consideration, where a small orthogonal magnetic field exist along the thin filament. A new Aharonov-Bohm (AB) phase term is obtained in the writhe number expression which is not present in the Moffatt-Ricca (Proc Roy Soc London A,1992) computation.

astro-ph↗