arXiv subjects

José A. C. Nogales

Publications and source records attributed to José A. C. Nogales.

12 recordsLinked to original sources

arXiv2026

Limits of the Rastall--Einstein Equivalence: Matter-Action Compatibility, FLRW Dynamics, and Exceptional Sectors

A regular Rastall metric equation can be written exactly as an Einstein equation with a conserved algebraic source. We examine whether this source redefinition also preserves a specified local matter-action class. For an isentropic barotropic fluid, keeping the particle-density variable and its conserved current fixed gives the compatibility condition $3nρ_{,nn}-ρ_{,n}=0$, whose non-Einstein solutions are $ρ(n)=ρ_Λ+C n^{4/3}$. For a minimally coupled first-derivative scalar field with the same field and kinetic variable, preservation of the local $\mathcal L_ϕ(X,ϕ)$ class gives $X\mathcal L_{ϕ,XX}-\mathcal L_{ϕ,X}=0$, and hence $\mathcal L_ϕ=\frac12\mathcal A(ϕ)X^2+\mathcal B(ϕ)$. These are off-shell functional compatibility tests within restricted continuum action classes; they do not by themselves establish equivalence of full solution spaces or observables. Throughout the analysis, $T_{μν}$ denotes the physical energy--momentum tensor of the specified matter model. Its Einstein-form algebraic image is $Θ_{μν}[T]=T_{μν}-αg_{μν}T$. We also complete the dictionary between two Ricci--trace parametrizations, including the coupling, and state a limited on-shell variational obstruction with its exceptions. The analysis includes Poisson-level weak-field matching for an operational rest-mass density, the singular FLRW branch $D(w)=0$, a classification of exceptional parameter sectors, and a comparison of Rastall gravity with standard unimodular gravity and nonconservative trace-free completions. The regular Rastall metric equation is therefore algebraically equivalent to an Einstein equation with a redefined source; equivalence of completed matter--gravity models is a separate, stronger requirement.

gr-qc↗

arXiv2025

Thermodynamics and Bouncing Cosmology in Rastall-like Gravity

In this study, we explore the thermodynamic aspects of a modified version of Rastall's gravity theory and its implications for cosmological scenarios. We analyze the role of non-conserved energy-momentum tensor equations and investigate their influence on particle production within an irreversible thermodynamic framework. By introducing a novel Lagrangian, we derive modified field equations and establish their relationship with matter production, both with and without entropy generation. Our analysis focuses on ideal fluid models and extends to spatially flat LFRW cosmologies, providing key equations that govern energy density, pressure, and curvature dynamics. Furthermore, we propose a bouncing cosmological model, in which the universe undergoes cycles of contraction and expansion, avoiding the singularity associated with the Big Bang. Our results indicate that this bouncing scenario is feasible within the Rastall-like gravity framework, supported by particle production processes and stability conditions. The violation of energy conditions near the bounce point further confirms the consistency of this alternative cosmological model. The present work is focused on the theoretical foundations and internal consistency of the model; possible observational implications will be addressed in future investigations. We conclude that the proposed theory offers a coherent phenomenological approach to matter production and provides new insights into non-standard cosmological evolution.

gr-qc↗

arXiv2021

Cosmology for high school

These notes on modern cosmology were made with high school teachers and students in mind. Taking into account the lack of availability of time and classes that many teachers have nowadays in Brazil, often caused by having to comply with very extensive subject curricula, performing various extra-class tasks and the tribulations inherent in the daily lives of all As workers in this country, we seek to develop basic topics and essentials about modern cosmology for your learning and consultation. We believe that, using it, you will be very well prepared to bring this very important theme of nature to the classroom. A differential of this didactic material is that each chapter has practical activities that allow us to fix the concepts of cosmology.

physics.ed-ph↗

arXiv2020

Wigner and Bell Inequalities relationships and Kolmogorov's Axioms

In this work, we show that Bell's inequality violation of arise from the fact that the condition imposed upon the development of inequality is not respected when it is applied in the idealized experiment. Such a condition is that the quantities taken by probability must be non negative, and such a condition is represented by $|\cal{P(w)}|=\cal{P(w)}$. We will also show that, when trying to define the values of the joint probabilities of $ (Z_1, Z_2, Z_3) $, through the values obtained from the $ (Z_j, Z_k) $ pairs, we find that these values are negative, so not Kolmogorov's axiom is respected: $\cal{P(w)}\geq0$ in cases where Bell's inequality is violated, and we also show that only such violation is possible if Wigner's inequality, in a certain arrangement, is violated, and that both violations are related to the violation of one of Kolmogorov's axioms. At the end of the paper, we suggest a new interpretation of the probabilities involved, in order to avoid the situation of negative probabilities and the violation of Bell's inequality and, consequently, Wigner's inequality.

quant-ph↗

arXiv2020

Gravitational entropy of wormholes with exotic matter and in galactic halos

In this work we study and compare the features of gravitational entropy near the throat of transversable wormholes formed by exotic matter and wormholes in galactic halos. We have verified that gravitational entropy and entropy density of these wormholes in regions near their throats are indistinguishable for objects of same throat, despite the fact they are described by different metrics and by distinct energy-momentum tensors. We have found that the gravitational entropy density diverges near the throat for both cases, probably due to a non-trivial topology at this point, however allowing the interesting interpretation that a maximum flux of information can be carried through the throat of these wormholes. In addition, we have found that both are endowed with an entropic behaviour similar to Hawking-Bekenstein's entropy of non-rotating and null charge black holes.

gr-qc↗

arXiv2020

Quantization of the interior of the black hole

In this work we study the Schwarzschild metric in the context of canonical quantum gravity inside the horizon, close of horizon and near the black hole singularity. Using this standard quantization procedure, we show that the horizon is quantized and the black hole singularity disappears. For the first case, quantization of the Schwarzschild radius was obtained in terms of the Planck length $l_{Pl}$, a positive integer $n$ and the ordering factor of the operator $p$. From the quantization of the Schwarzschild radius it was possible to determine the area of the black hole event horizon, its mass and the quantum energy of the Hawking radiation as well as its frequency. For the solution close to the interior black hole singularity, the wave function was determined and applied the DeBroglie-Bohm interpretation. The Bohm's trajectory was found near to the singularity. It which describes how the spacetime evolves over time and depends on the ordering factor of the operator $p$. Thus, for the case where $|1-p|\neq0,3$, the Bohm's trajectory is finite and regular, that is, the singularity is removed. For the case where $|1-p|=3$, the Bohm's trajectory assumes an exponential behavior, never going to zero, avoiding the singularity.That result allows that spacetime be extended beyond the classical singularity.

gr-qc↗

arXiv2018

The Clauser-Horne-Shimony-Holt inequality in the context of a broad random variable

In this work we aim to analyze the Clauser-Horne-Shimony-Holt CHSH inequality strictly in the context of probability theory. In the course of assembling inequality we have to take care not to produce assumptions a priori, that is, physically or intuitively accepted suppositions. Of course, this does not mean that after these considerations, we put the adequate physical conditions suitable and generally accepted in these contexts. This allows us to clearly visualize the possibility of finding a greater inequality than that of CHSH in which it is included. This inequality does not contradict the CHSH inequality. This result is suported by using a robust computational simulation, showing the possibility for obtaining an inequality for quantum mechanics that is not violated and allows random hidden variables without any conflict with Bell's inequality.

quant-ph↗

arXiv2017

Cosmology from a Lagrangian formulation for Rastall's theory

We give a Lagrangian formulation for the theory of Rastall of gravitation. After proposing a Lagrangian density that reproduces the equations of motion postulated by Rastall, we study the cosmological consequences and fit the parameters using recent data from Hubble function $H(z).$ According to two model selection criteria, one based on corrected Akaike Information Criterion (AICc) and another on Bayesian Information Criterion (BIC), known to penalize models with a greater number of parameters, particularly BIC, we obtain some competitive models relative do $ΛCDM.$ In one of these models the cosmological constant is interpreted as having origin in the creation of matter due to time dependent gravitational field, as opposed to the origin in the vacuum energy.

gr-qc↗

arXiv2016

Violation of probabilistic inequality Clauser-Horne-Shimony-Holt in Quantum Mechanics

In 1982, Alain Aspect, and collaborators performed an experiment, in order to observe the violation of the inequality of Clauser-Horne-Shimony-Holt. After the experiment, they used the data in the inequality and concluded that the inequality, obtained through probabilistic arguments, was violated confirming the conclusions obtained by John S. Bell that was not possible a theory of hidden variables in the conditions suggested by Einstein, Podolsky and Rosen. The aim of this work is to verify the validity of the inequalities in the conditions of the probabilistic theory, in order to hold with the axioms of the probability.

physics.gen-ph↗

arXiv2015

Quantum Hořava-Lifshitz cosmology and the quantum nature of coupling corrections of HL gravity

In this work were studied quantum models of a Friedmann-Robertson-Walker (FRW) cosmology in the framework of the gravity's theory proposed by Hořava, the so-called Hořava-Lifshitz theory of the gravity. It was used the Hořava theory for the projectable Hořava-Lifshitz (HL) gravity without the detailed balance condition. Following the quantization of the model in the context of Wheeler-DeWitt approach and taking in account the ordering factor for operators were found the cosmological wave function. Solutions were studied and the results were discussed for some particular cases close of initial singularity. The resulting wave functions were used to investigate the possibility of to avoid the classical singularities due to quantum effects and for analyzing the entanglement entropy. In the ultraviolet phase were found the existence of cosmological wave function with a relation between the ordering factor and coupling constants showing their quantum nature, then it was possible to provide an explicit evolution of the cosmological entanglement entropy in this stage. The interpretation of Bohm-De Broglie was used to discussion of the solutions.

gr-qc↗

arXiv2013

The dynamics of a rotating ellipsoid

An interesting physical phenomenon, which contradicts our common sense, is concerned with the dynamics of motion of a spinning ellipsoid in a non smooth surface. A hard-boiled egg spinning on a table with a rough surface is an example. In this article, we present a theoretical explanation, of the dynamics of motion of this ellipsoid, that describes the axis raising phenomenon, from the horizontal to the vertical. The equations of motion were obtained with Lagrangian formalism.

physics.ed-ph↗

arXiv1998

Instability of cosmological event horizons of nonstatic global cosmic strings II: perturbations of gravitational waves and massless scalar field

The stability of the cosmological event horizons (CEHs) of a class of non-static global cosmic strings is studied against perturbations of gravitational waves and massless scalar field. It is found that the perturbations of gravitational waves always turn the CEHs into non-scalar weak spacetime curvature singularities, while the ones of massless scalar field turn the CEHs either into non-scalar weak singularities or into scalar ones depending on the particular cases considered. The perturbations of test massless scalar field is also studied, and it is found that they do not always give the correct prediction.

gr-qc↗