776 research outputs found
Creation of spin 1/2 particles by an electric field in de Sitter space
In the present article we solve the Dirac equation in a de Sitter universe
when a constant electric field is present. Using the Bogoliubov
transformations, we compute the rate of spin 1/2 created particles by the
electric field. We compare our results with the scalar case. We also analyze
the behavior of the density of particles created in the limit H=0, when de
Sitter background reduces to a flat space-time.Comment: 10 pages, REVTEX, no figure
Dirac spinor in a nonstationary Godel-type cosmological Universe
In the present article we solve, via separation of variables, the massless
Dirac equation in a nonstationary rotating, causal G\"odel-type cosmological
universe, having a constant rotational speed in all the points of the space. We
compute the frequency spectrum. We show that the spectrum of massless Dirac
particles is discrete and unbounded.Comment: 6pp, IVIC-CFLE 93/0
Analytic Solution of a Relativistic Two-dimensional Hydrogen-like Atom in a Constant Magnetic Field
We obtain exact solutions of the Klein-Gordon and Pauli Schroedinger
equations for a two-dimensional hydrogen-like atom in the presence of a
constant magnetic field. Analytic solutions for the energy spectrum are
obtained for particular values of the magnetic field strength. The results are
compared to those obtained in the non-relativistic and spinless case. We obtain
that the relativistic spectrum does not present s states.Comment: RevTeX, 8 pages, to be published in Phys. Lett.
Scattering of a relativistic scalar particle by a cusp potential
We solve the Klein-Gordon equation in the presence of a spatially
one-dimensional cusp potential. The scattering solutions are obtained in terms
of Whittaker functions and the condition for the existence of transmission
resonances is derived. We show the dependence of the zero-reflection condition
on the shape of the potential. In the low momentum limit, transmission
resonances are associated with half-bound states. We express the condition for
transmission resonances in terms of the phase shifts.Comment: To appear in Physics Letters
Creation of scalar and Dirac particles in the presence of a time varying electric field in an anisotropic Bianchi I universe
In this article we compute the density of scalar and Dirac particles created
by a cosmological anisotropic Bianchi type I universe in the presence of a time
varying electric field. We show that the particle distribution becomes thermal
when one neglects the electric interaction.Comment: 8 pages, REVTEX 3.0. to appear in Phys. Rev.
Calculation of the energy spectrum of a two-electron spherical quantum dot
We study the energy spectrum of the two-electron spherical parabolic quantum
dot using the exact Schroedinger, the Hartree-Fock, and the Kohn-Sham
equations. The results obtained by applying the shifted-1/N method are compared
with those obtained by using an accurate numerical technique, showing that the
relative error is reasonably small, although the first method consistently
underestimates the correct values. The approximate ground-state Hartree-Fock
and local-density Kohn-Sham energies, estimated using the shifted-1/N method,
are compared with accurate numerical self-consistent solutions. We make some
perturbative analyses of the exact energy in terms of the confinement strength,
and we propose some interpolation formulae. Similar analysis is made for both
mean-field approximations and interpolation formulae are also proposed for
these exchange-only ground-state cases.Comment: 18 pages, LaTeX, 2 figures-ep
Exact solution of the two-dimensional Dirac oscillator
In the present article we have found the complete energy spectrum and the
corresponding eigenfunctions of the Dirac oscillator in two spatial dimensions.
We show that the energy spectrum depends on the spin of the Dirac particle.Comment: revtex, 6pp. IVIC-CFLE 93/0
Electrically neutral Dirac particles in the presence of external fields: exact solutions
In the present article we present exact solutions of the Dirac equation for
electric neutral particles with anomalous electric and magnetic moments. Using
the algebraic method of separation of variables, the Dirac equation is
separated in cartesian, cylindrical and spherical coordinates, and exact
solutions are obtained in terms of special functions.Comment: 20pp, IVIC-CFLE-93/02 (this is a version without Tex problems, the
first version was corrupted
Scattering of a Klein-Gordon particle by a Woods-Saxon potential
We solve the Klein-Gordon equation in the presence of a spatially
one-dimensional Woods-Saxon potential. The scattering solutions are obtained in
terms of hypergeometric functions and the condition for the existence of
transmission resonances is derived. It is shown how the zero-reflection
condition depends on the shape of the potential.Comment: 10 pages, Revtex. To appear in Phys. Rev.
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