arXiv subjects
Publications and source records attributed to E. Capelas de Oliveira.
We use the definition of a fractional integral, recently proposed by Katugampola, to establish a generalization of the reverse Minkowski's inequality. We show two new theorems associated with this inequality, as well as state and show other inequalities related to this fractional operator.
The relaxation functions introduced empirically by Debye, Cole-Cole, Cole-Davidson and Havriliak-Negami are, each of them, solutions to their respective kinetic equations. In this work, we propose a generalization of such equations by introducing a fractional differential operator written in terms of the Riemann-Liouville fractional derivative of order $γ$, $0 < γ\leq 1$. In order to solve the generalized equations, the Laplace transform methodology is introduced and the corresponding solutions are then presented, in terms of Mittag-Leffler functions. In the case in which the derivative's order is $γ=1$, the traditional relaxation functions are recovered. Finally, we presente some 2D graphs of these function.
Using the fractional derivative, considered in the Caputo sense, we study an analytical technique associated with the variational iteration method for the fractional generalized $α$-time Burgers' equation with $α>0$ and obtain approximate solutions in particular cases $0<α\leq 1$ and $1<α\leq 2$.
In this paper we recall that by construction Elko spinor fields of λ and ρ types satisfy a coupled system of first order partial differential equations (csfopde) that once interacted leads to Klein-Gordon equations for the λ and ρ type fields. Since the csfopde is the basic one and since the Klein-Gordon equations for λ and ρ possess solutions that are not solutions of the csfopde for λ and ρ we infer that it is legitimate to attribute to those fields mass dimension 3/2 (as is the case of Dirac spinor fields) and not mass dimension 1 as previously suggested in recent literature (see list of references). A proof of this fact is offered by deriving the csfopde for the λ and ρ from a Lagrangian where these fields have indeed mass dimension 3/2. Taking seriously the view that Elko spinor fields due to its special properties given by their bilinear invariants may be the description of some kind of particles in the real world a question then arises: what is the physical meaning of these fields? Here we proposed that the fields λ and ρ serve the purpose of building the fields K and M (see Eq.(38))which are Clifford valued multiform fields representing spinor fields in the Clifford bundle. They are electrically neutral and do not couple to the electromagnetic field but carry magnetic like charges which permit them to couple to a su(2) valued potential. If the potential is of short range the particles described by the K and M fields may be interacting and forming condensates of zero spin particles analogous to dark matter, in the sense that they do not couple with the electromagnetic field (generated by charged particles) and are thus invisible. We calculate the correct propagators for the K and M fields. We discuss also the main difference between Elko and Majorana spinor fields.
In a previous paper we showed that Weyl equation possess superluminal solutions and moreover we showed that those solutions that are eigenstates of the parity operator seem to describe a coupled pair of a monopole anti-monopole system. This result suggests to look for a solution of Maxwell equation \partialF^{\infty}=-gJ with a current J as source and such that the Lorentz force on the current is null. We first identify a solution where J=γ^{5}J_{m}is a spacelike field (even if F is not a superluminal solution of the homogeneous Maxwell equation). More surprisingly we find that there exists a solution F of the free Maxwell \partialF=0 that is equivalent to the non homogeneous equation for F^{\infty}. Once this result is proved it suggests by itself to look for more general subluminal and superluminal solutions F of the free Maxwell equation equivalent to a non homogeneous Maxwell equation for a field F_{0} with a current term as source which may be subluminal or superluminal. We exhibit one such subluminal solution, for which the Dirac-Hestenes spinor field ψ associated the electromagnetic field F_{0} satisfies a Dirac equation for a bradyonic neutrino under the ansatz that the current is ce^{λγ^{5}}gψγ^{0}ψ, with g the quantum of magnetic charge and λ a constant to be determined in such a way that the auto-force be null. Together with Dirac's quantization condition this gives a quantized mass spectrum (Eq.49) for the neutrinos, with the masses of the different flavor neutrinos being of the same order of magnitude (Eq.50) which is in accord with recent experimental findings. As a last surprise we show that the mass spectrum found in the previous case continues to hold if the current is taken spacelike, i.e., ce^{λγ^{5}}gψ_{>}γ^{3}ψ_{>} with ψ_{>}, in this case, satisfying a tachyonic Dirac-Hestenes equation.
By analyzing the structure of the Weyl spinor field in the Clifford bundle formalism we show that in each spinorial frame it is represented by F\insec(\doublebarwedge^0 T^\starM + \doublebarwedge^2 T^\star M + \doublebarwedge^{4} T^\star M)\hookrightarrowsecC\ell(M,g) satisfying the equation \partialF=0, where \partial is the Dirac operator acting on sections of the Clifford bundle C\ell(M,g). With this result we show that introducing a generalized potential A=(A + γ_5 B)\insec(\doublebarwedge^{1}T^{\star}M + \doublebarwedge^3 T^\star M)\hookrightarrowsecC\ell(M,g) for the Weyl field such that F=\partialA it is possible to exhibit superluminal solutions (including one with a front moving at superluminal speed) for Weyl equation, which surprisingly describes the propagation of a massive tachyonic neutrino. We propose to interpret these extraordinary solutions in order that eventually they may serve as possible models for the emission process and propagation of the superluminal neutrinos observed at the OPERA experiment. Moreover, complementing this study we show that general local chiral invariance of Weyl equation implies that it describes for all solutions that are eigenstates of the parity operator a pair of `sub-particles' carrying opposite magnetic charges (thus possibly carrying a small magnetic moment) which thus interact with an external electromagnetic field. Even if at the Earth's electromagnetic field the effect may result negligible, eventually the idea may be a useful one to study neutrinos leaving the electromagnetic field of stars.
In this paper we analyze the status of some `unbelievable results' presented in the paper `On Some Contradictory Computations in Multi-Dimensional Mathematics' [1] published in Nonlinear Analysis, a journal indexed in the Science Citation Index. Among some of the unbelievable results `proved' in the paper we can find statements like that: (i) a linear transformation which is a rotation in R^2 with rotation angle theta different from nphi/2, is inconsistent with arithmetic, (ii) complex number theory is inconsistent. Besides these 'results' of mathematical nature [1],offers also a `proof' that Special Relativity is inconsistent. Now, we are left with only two options (a) the results of [1] are correct and in this case we need a revolution in Mathematics (and also in Physics) or (b) the paper is a potpourri of nonsense. We show that option (b) is the correct one. All `proofs' appearing in [1] are trivially wrong, being based on a poor knowledge of advanced calculus notions. There are many examples (some of them discussed in [2,3,4,5,6]of complete wrong papers using nonsequitur Mathematics in the Physics literature. Taking into account also that a paper like [1] appeared in a Mathematics journal we think that it is time for editors and referees of scientific journals to become more careful in order to avoid the dissemination of nonsense.
This work is intended to investigate the geometry of anti-de Sitter spacetime (AdS), from the point of view of the Laplacian Comparison Theorem (LCT), and to give another description of the hyperbolical embedding standard formalism of the de Sitter and anti-de Sitter spacetimes in a pseudo-Euclidean spacetime. It is shown how to reproduce some geometrical properties of AdS, from the LCT in AdS, choosing suitable functions that satisfy basic properties of Riemannian geometry. We also introduce and discuss the well-known embedding of a 4-sphere and a 4-hyperboloid in a 5-dimensional pseudo-Euclidean spacetime, reviewing the usual formalism of spherical embedding and the way how it can retrieve the Robertson-Walker metric. With the choice of the de Sitter metric static frame, we write the so-called reduced model in suitable coordinates. We assume the existence of projective coordinates, since de Sitter spacetime is orientable. From these coordinates, obtained when stereographic projection of the de Sitter 4-hemisphere is done, we consider the Beltrami geodesic representation, which gives a more general formulation of the seminal full model described by Schrodinger, concerning the geometry and the topology of de Sitter spacetime. Our formalism retrieves the classical one if we consider the metric terms over the de Sitter splitting on Minkowski spacetime. From the covariant derivatives we find the acceleration of moving particles, Killing vectors and the isometry group generators associated to de the Sitter spacetime.
Using conformal coordinates associated with conformal relativity -- associated with de Sitter spacetime homeomorphic projection into Minkowski spacetime -- we obtain a conformal Klein-Gordon partial differential equation, which is intimately related to the production of quasi-normal modes (QNMs) oscillations, in the context of electromagnetic and/or gravitational perturbations around, e.g., black holes. While QNMs arise as the solution of a wave-like equation with a Poschl-Teller potential, here we deduce and analytically solve a conformal radial d'Alembert-like equation, from which we derive QNMs formal solutions, in a proposed alternative to more completely describe QNMs. As a by-product we show that this radial equation can be identified with a Schrodinger-like equation in which the potential is exactly the second Poschl-Teller potential, and it can shed some new light on the investigations concerning QNMs.
We revisit the investigation about the partition function related to a ϕ^4-scalar field theory on a n-dimensional Minkowski spacetime, which is shown to be a self-interacting scalar field theory at least in 4-dimensional Minkowski spacetime. After rederiving the analytical calculation of the perturbative expansion coefficients and also the approximate values for suitable limits using Stirling's formulae, which consists of Witten's proposed questions, solved by P. Deligne, D. Freed, L. Jeffrey, and S. Wu, we investigate a spherically symmetric scalar field in a n-dimensional Minkowski spacetime. For the first perturbative expansion coefficient it is shown how it can be derived a modified Bessel equation (MBE), which solutions are investigated in one, four, and eleven-dimensional Minkowski spacetime. The solutions of MBE are the first expansion coefficient of the series associated with the partition function of ϕ^4-scalar field theory. All results are depicted.
Using conformal coordinates associated with projective conformal relativity we obtain a conformal Klein-Gordon partial differential equation. As a particular case we present and discuss a conformal `radial' d'Alembert-like equation. As a by-product we show that this `radial' equation can be identified with a one-dimensional Schrödinger-like equation in which the potential is exactly the second Pöschl-Teller potential.
In this paper we show how to describe the general theory of a linear metric compatible connection with the theory of Clifford valued differential forms. This is done by realizing that for each spacetime point the algebra of Clifford bivectors is isomorphic to the Lie algebra of Sl(2,C). In that way the pullback of the linear connection under a trivialization of the bundle is represented by a Clifford valued 1-form. That observation makes it possible to realize Einstein's gravitational theory can be formulated in a way which is similar to a Sl(2,C) gauge theory. Some aspects of such approach is discussed. Also, the theory of the covariant spinor derivative of spinor fields is introduced in a novel way, allowing for a physical interpretation of some rules postulated for that covariant spinor derivative in the standard theory of these objects. We use our methods to investigate some polemical issues in gravitational theories and in particular we scrutinize a supposedly "unified" field theory of gravitation and electromagnetism proposed by M. Sachs and recently used in a series of papers. Our results show that Sachs did not attain his objective and that recent papers based on that theory are ill conceived and completely invalid both as Mathematics and Physics.
We investigate using Clifford algebra methods the theory of algebraic dotted and undotted spinor fields over a Lorentzian spacetime and their realizations as matrix spinor fields, which are the usual dotted and undotted two component spinor fields. We found that some ad hoc rules postulated for the covariant derivatives of Pauli sigma matrices and also for the Dirac gamma matrices in General Relativity cover important physical meaning, which is not apparent in the usual matrix presentation of the theory of two components dotted and undotted spinor fields. We also discuss some issues related to the the previous one and which appear in a proposed "unified" theory of gravitation and electromagnetism which use two components dotted and undotted spinor fields and also paravector fields, which are particular sections of the even subundle of the Clifford bundle of spacetime.
We exhibit exact finite energy superluminal solutions of Maxwell equations in vacuum.
In this paper we present thoughtful comments on the paper `Bessel beams and signal propagation' showing that the main claims of that paper are wrong. Moreover, we take the opportunity to show the non trivial and indeed surprising result that a scalar pulse (i.e., a wave train of compact support in the time domain) that is solution of the homogeneous wave equation (vector ($\vec{E},\vec{B}$) pulse that is solution of Maxwell equations) is such that its {\em wave front} in some cases does travel with speed {\em greater} than $c$, the speed of light . In order for a pulse to posses a front that travels with speed $c$, an additional condition must be satisfied, namely the pulse must have finite energy. When this condition is fulfilled the pulse still can show peaks propagating with superluminal (or subluminal) velocities, but now its wave front travels at speed $c$. These results are important because they explain several experimental results obtained in recent experiments, where superluminal velocities have been observed, without implying in any breakdown of the Principle of Relativity.