arXiv subjects

F. N. Lima

Publications and source records attributed to F. N. Lima.

4 recordsLinked to original sources

arXiv2020

Absence of eigenvalues in the continuous spectrum for Klein-Gordon operators

We construct the one-dimensional analogous of von-Neumann Wigner potential to the relativistic Klein-Gordon operator, in which is defined taking asymptotic mathematical rules in order to obtain existence conditions of eigenvalues embedded in the continuous spectrum. Using our constructed potential, we provide an explicit and analytical example of the Klein-Gordon operator with positive eigenvalues embedded in the so called relativistic "continuum region". Even so in this not standard example, we present the region of the "continuum" where those eigenvalues cannot occur. Besides, the absence of eigenvalues in the continuous spectrum for Klein-Gordon operators is proven to a broad general potential classes, including the minimally coupled electric Coulomb potential. Considering known techniques available in literature for Schrodinger operators, we demonstrate an expression for Klein-Gordon operator written in Schrodinger's form, whereby is determined the mathematical spectrum region of absence of eigenvalues.

math-ph↗

arXiv2020

An exact solution of the orbit equation for a massive particle in Schwarzschild metric

In this paper, we consider a spherically curved symmetric spacetime to exact solving the orbit equation of a massive particle by using Jacobi's elliptic functions. Generally, the solution of the orbit equation provides the relativistic effects on the massive particle, absents in Newtonian mechanics. Besides, we investigate the additional physical information introduced by the exact solution to the orbit equation that is not visible in the approximate solutions traditionally presented in literature. Here, we exactly solve the problem by the use an analytical methodology step by step in order to provide detailed solutions as well as demonstrate with mathematical rigour the geodesic solution in terms of Jacobi's elliptic functions. We find oscillatory movements of the orbit of the massive particle at the expected regimes without to consider any heuristic argument. Bound regions to the solution of the equation of motion is presented, finding the aspect of the geodesic when the massive particle is trapped in the gravitational field of the source.

gr-qc↗

arXiv2019

Mass spectrum of scalar and gauge fields in the cosmological multiply warped brane-world

In this paper, we compute the massive modes of scalar and gauge fields in a multiply warped brane-world scenario in six-dimensional spacetime with a Freedman-Robertson-Walker (FRW) metric. The massive Kaluza-Klein (KK) modes of the fields are split in two mass towers due to the presence of the warped in both dimensions. This does not occurs in the standard Randall-Sundrum (RS) model. We investigate the dependence of the mass spectrum on Hubble constant. Lighter massive modes of the fields are found, whereby it is possible to infer that scalar and bosonic matter can directly influence in universe expansion.

gr-qc↗

arXiv2019

Mathematical methods of diagonalization of quadratic forms applied to the study of stability of thermodynamic systems

In this paper, we use quadratic forms diagonalization methods applied to the function thermodynamic energy to analyze the stability of physical systems. Taylor's expansion was useful to write a quadratic expression for the energy function. We consider the same methodology to expanding the thermodynamic entropy and investigate the signs of the second-order derivatives of the entropy as well as previously to the thermodynamic energy function. The signs of the second-order derivatives to the Helmholtz, enthalpy and Gibbs functions are also analysed. We show the immediate consequences on the stability of physical systems due to the signs or curvatures of the second-order derivatives of these thermodynamic functions. The thermodynamic potentials are presented and constructed pedagogically as well as demonstrated the main mathematical aspects these surfaces. We demonstrate the power of superposition of mathematical and physical aspects to understand the stability of thermodynamic systems. Besides, we provide a consistent mathematical demonstration of the minimum, maximum, and saddle conditions of the potentials. We present here a detailed approach on aspects related to the curvature of the thermodynamic functions of physical interest with consequences on stability. This work can be useful as a part or supplement material of the traditional physics curriculum that requires a solid formation in thermodynamics, particularly about formal aspects on the stability.

cond-mat.stat-mech↗