Percorrer por autor "Vieira, Nelson"
A mostrar 1 - 10 de 13
Resultados por página
Opções de ordenação
- Application of the Fractional Sturm–Liouville Theory to a Fractional Sturm–Liouville Telegraph EquationPublication . Ferreira, M.; Rodrigues, M. Manuela; Vieira, NelsonIn this paper, we consider a non-homogeneous time-space-fractional telegraph equation in n-dimensions, which is obtained from the standard telegraph equation by replacing the first- and second-order time derivatives by Caputo fractional derivatives of corresponding fractional orders, and the Laplacian operator by a fractional Sturm-Liouville operator defined in terms of right and left fractional Riemann-Liouville derivatives. Using the method of separation of variables, we derive series representations of the solution in terms of Wright functions, for the homogeneous and non-homogeneous cases. The convergence of the series solutions is studied by using well known properties of the Wright function. We show also that our series can be written using the bivariate Mittag-Leffler function. In the end of the paper, some illustrative examples are presented.
- First and second fundamental solutions of the time-fractional telegraph equation of order 2αPublication . Ferreira, Milton; Rodrigues, M. Manuela; Vieira, NelsonIn this work we obtain the first and second fundamental solutions of the multidimensional time-fractional equation of order 2α, α ∈]0, 1], where the two time-fractional derivatives are in the Caputo sense. We obtain representations of the fundamental solutions in terms of Hankel transform, double Mellin-Barnes integral, and H-functions of two variables. As an application, the fundamental solutions are used to solve a Cauchy problem and to study telegraph process with Brownian time.
- First and second fundamental solutions of the time-fractional telegraph equation with Laplace or Dirac operatorsPublication . Ferreira, Milton; Rodrigues, Manuela M.; Vieira, NelsonIn this work we obtain the first and second fundamental solutions (FS) of the multidimensional time-fractional equation with Laplace or Dirac operators, where the two time-fractional derivatives of orders α ∈]0, 1] and β ∈]1, 2] are in the Caputo sense. We obtain representations of the FS in terms of Hankel transform, double Mellin- Barnes integrals, and H-functions of two variables. As an application, the FS are used to solve Cauchy problems of Laplace and Dirac type.
- A Fractional Analysis in Higher Dimensions for the Sturm-Liouville ProblemPublication . Ferreira, Milton; Rodrigues, M. Manuela; Vieira, NelsonIn this work, we consider the n-dimensional fractional Sturm-Liouville eigenvalue problem, by using fractional versions of the gradient operator involving left and right Riemann-Liouville fractional derivatives. We study the main properties of the eigenfunctions and the eigenvalues of the associated fractional boundary problem. More precisely, we show that the eigenfunctions are orthogonal and the eigenvalues are real and simple. Moreover, using techniques from fractional variational calculus, we prove in the main result that the eigenvalues are separated and form an infinite sequence, where the eigenvalues can be ordered according to increasing magnitude. Finally, a connection with Clifford analysis is established.
- Fundamental Solution of the Multi-Dimensional Time Fractional Telegraph EquationPublication . Ferreira, Milton; Rodrigues, M. Manuela; Vieira, NelsonIn this paper we study the fundamental solution (FS) of the multidimensional time-fractional telegraph equation where the time-fractional derivatives of orders α ∈]0,1] and β ∈]1,2] are in the Caputo sense. Using the Fourier transform we obtain an integral representation of the FS in the Fourier domain expressed in terms of a multivariate Mittag-Leffler function. The Fourier inversion leads to a double Mellin-Barnes type integral representation and consequently to a H-function of two variables. An explicit series representation of the FS, depending on the parity of the dimension, is also obtained. As an application, we study a telegraph process with Brownian time. Finally, we present some moments of integer order of the FS, and some plots of the FS for some particular values of the dimension and of the fractional parameters α and β.
- Fundamental solution of the time-fractional telegraph Dirac operatorPublication . Ferreira, Milton; Rodrigues, M. Manuela; Vieira, Nelsonn this work, we obtain the fundamental solution (FS) of the multidimensionaltime-fractional telegraph Dirac operator where the 2 time-fractional derivatives oforders𝛼∈]0,1]and𝛽∈]1,2]are in the Caputo sense. Explicit integral and seriesrepresentation of the FS are obtained for any dimension. We present and discusssome plots of the FS for some particular values of the dimension and of the frac-tional parameters𝛼and𝛽. Finally, using the FS, we study some Poisson and Cauchyproblems
- Multidimensional fractional Schrödinger equationPublication . Rodrigues, M. M.; Vieira, NelsonThis work is intended to investigate the multi-dimensional space-time fractional Schrödinger equation of the form ħ𝛻 , with ħ the Planck's constant divided by 2π, m is the mass and u(t,x) is a wave function of the particle. Here 𝛻 are operators of the Caputo fractional derivatives, where α ∈]0,1] and β ∈]1,2]. The wave function is obtained using Laplace and Fourier transforms methods and a symbolic operational form of solutions in terms of the Mittag-Leffler functions is exhibited. It is presented an expression for the wave function and for the quantum mechanical probability density. Using Banach fixed point theorem, the existence and uniqueness of solutions is studied for this kind of fractional differential equations.
- On a regular Ψ-fractional Sturm-Liouville problemPublication . Ferreira, M.; Rodrigues, M. Manuela; Vieira, NelsonIn this short paper, we consider a $\psi$-fractional Sturm-Liouville eigenvalue problem by using left $\psi$-Caputo and right $\psi$-Riemann-Liouville fractional derivatives. We study the main properties of the eigenfunctions and the eigenvalues of the associated fractional boundary problem.
- Some representations for the eigenfunctions of the time-fractional wave operatorPublication . Rodrigues, M.M.; Ferreira, M.; Vieira, NelsonIn this work we present some new representations for the eigenfunctions of the time-fractional wave operator with the time-fractional derivative in the Caputo sense.
- Time-fractional diffusion equation with psi-Hilfer derivativePublication . Vieira, Nelson; Rodrigues, M. Manuela; Ferreira, MiltonIn this work, we consider the multidimensional time-fractional diffusion equation with the $\psi$-Hilfer derivative. This fractional derivative enables the interpolation between Riemann-Liouville and Caputo fractional derivatives and its kernel depends on an arbitrary positive monotone increasing function $\psi$ thus encompassing several fractional derivatives in the literature. This allows us to obtain general results for different families of problems that depend on the function $\psi$ selected. By employing techniques of Fourier, $\psi$-Laplace, and Mellin transforms, we obtain a solution representation in terms of convolutions involving Fox H-functions for the Cauchy problem associated with our equation. Series representations of the first fundamental solution are explicitly obtained for any dimension as well as the fractional moments of arbitrary positive order. For the one-dimensional case, we show that the series representation reduces to a Wright function, and we prove that it corresponds to a probability density function for any admissible $\psi$. Finally, some plots of the fundamental solution are presented for particular choices of the function $\psi$ and the order of differentiation.