3,328 research outputs found
Semi-spectral Chebyshev method in Quantum Mechanics
Traditionally, finite differences and finite element methods have been by
many regarded as the basic tools for obtaining numerical solutions in a variety
of quantum mechanical problems emerging in atomic, nuclear and particle
physics, astrophysics, quantum chemistry, etc. In recent years, however, an
alternative technique based on the semi-spectral methods has focused
considerable attention. The purpose of this work is first to provide the
necessary tools and subsequently examine the efficiency of this method in
quantum mechanical applications. Restricting our interest to time independent
two-body problems, we obtained the continuous and discrete spectrum solutions
of the underlying Schroedinger or Lippmann-Schwinger equations in both, the
coordinate and momentum space. In all of the numerically studied examples we
had no difficulty in achieving the machine accuracy and the semi-spectral
method showed exponential convergence combined with excellent numerical
stability.Comment: RevTeX, 12 EPS figure
An integral equation method for solving neumann problems on simply and multiply connected regions with smooth boundaries
This research presents several new boundary integral equations for the solution of Laplaceâs equation with the Neumann boundary condition on both bounded and unbounded multiply connected regions. The integral equations are uniquely solvable Fredholm integral equations of the second kind with the generalized Neumann kernel. The complete discussion of the solvability of the integral equations is also presented. Numerical results obtained show the efficiency of the proposed method when the boundaries of the regions are sufficiently smooth
Fast integral equation methods for the modified Helmholtz equation
We present a collection of integral equation methods for the solution to the
two-dimensional, modified Helmholtz equation, u(\x) - \alpha^2 \Delta u(\x) =
0, in bounded or unbounded multiply-connected domains. We consider both
Dirichlet and Neumann problems. We derive well-conditioned Fredholm integral
equations of the second kind, which are discretized using high-order, hybrid
Gauss-trapezoid rules. Our fast multipole-based iterative solution procedure
requires only O(N) or operations, where N is the number of nodes
in the discretization of the boundary. We demonstrate the performance of the
methods on several numerical examples.Comment: Published in Computers & Mathematics with Application
Wiener-Hopf solution for impenetrable wedges at skew incidence
A new Wiener-Hopf approach for the solution of impenetrable wedges at skew incidence is presented. Mathematical aspects are described in a unified and consistent theory for angular region problems. Solutions are obtained using analytical and numerical-analytical approaches. Several numerical tests from the scientific literature validate the new technique, and new solutions for anisotropic surface impedance wedges are solved at skew incidence. The solutions are presented considering the geometrical and uniform theory of diffraction coefficients, total fields, and possible surface wave contribution
Emergent bubbling geometries in gauge theories with SU(2|4) symmetry
We study the gauge/gravity duality between bubbling geometries in type IIA
supergravity and gauge theories with SU(2|4) symmetry, which consist of N=4
super Yang-Mills on , N=8 super Yang-Mills on
and the plane wave matrix model. We show that the geometries are realized as
field configurations in the strong coupling region of the gauge theories. On
the gravity side, the bubbling geometries can be mapped to electrostatic
systems with conducting disks. We derive integral equations which determine the
charge densities on the disks. On the gauge theory side, we obtain a matrix
integral by applying the localization to a 1/4-BPS sector of the gauge
theories. The eigenvalue densities of the matrix integral turn out to satisfy
the same integral equations as the charge densities on the gravity side. Thus
we find that these two objects are equivalent.Comment: 29 pages, 3 figures; v2: typos corrected and a reference adde
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