Oktay Aydogdu

Dirac particles in the presence of the Yukawa potential plus a tensor interaction in SUSYQM framework

Applying an appropriate approximation scheme to deal with the centrifugal term, pseudospin and spin symmetric solutions of the Dirac–Yukawa problem with tensor interaction are investigated based on supersymmetric quantum mechanics (SUSYQM) and shape invariance (SI) formalism. We show that the energy eigenvalues equation is simply obtained by using the methodology of SUSYQM and SI. The corresponding wave functions are obtained in terms of hypergeometric functions. Effects of tensor interaction on the bound states and eigenfunctions are also investigated numerically. Further, we compare our results with those given in the literature, which are obtained by using the Nikiforov–Uvarov and asymptotic iteration methods.

Dirac equation for the Hulthén potential within the Yukawa-type tensor interaction

Using the Nikiforov?Uvarov (NU) method, pseudospin and spin symmetric solutions of the Dirac equation for the scalar and vector Hulth?n potentials with the Yukawa-type tensor potential are obtained for an arbitrary spin?orbit coupling quantum number ?. We deduce the energy eigenvalue equations and corresponding upper- and lower-spinor wave functions in both the pseudospin and spin symmetry cases. Numerical results of the energy eigenvalue equations and the upper- and lower-spinor wave functions are presented to show the effects of the external potential and particle mass parameters as well as pseudospin and spin symmetric constants on the bound-state energies and wave functions in the absence and presence of the tensor interaction.

Solution of the Dirac equation for pseudoharmonic potential by using the Nikiforov–Uvarov method

We investigate the energy spectra and corresponding wave functions of the Dirac equation for pseudoharmonic potential with spin and pseudospin symmetry. To obtain an analytical solution of the Dirac equation, we consider the Nikiforov–Uvarov method in the calculations. For any spin–orbit coupling term κ, we find the closed forms of the energy eigenvalues and also obtain the radial wave functions in the spin and pseudospin symmetry limits.

The Dirac–Yukawa problem in view of pseudospin symmetry

An approximate analytical solution of the Dirac equation for the Yukawa potential under the pseudospin symmetry condition is obtained using the asymptotic iteration method. We discover the energy eigenvalue equation and some of the numerical results are listed. Wave functions are obtained in terms of hypergeometric functions. Extra degeneracies are removed by adding a new term, A/r2, to the Yukawa potential. The effects of tensor interaction on the two states in the pseudospin doublet are also investigated.

Scattering and bound state solutions of the asymmetric Hulthén potential

The one-dimensional time-independent Schrodinger equation is solved for the asymmetric Hulthen potential. The reflection and transmission coefficients and bound state solutions are obtained in terms of the hypergeometric functions. It is observed that the unitary condition is satisfied in the non-relativistic region.

Effective-mass Dirac equation for Woods-Saxon potential: Scattering, bound states, and resonances

Approximate scattering and bound state solutions of the one-dimensional effective-mass Dirac equation with the Woods-Saxon potential are obtained in terms of the hypergeometric-type functions. Transmission and reflection coefficients are calculated by using behavior of the wave functions at infinity. The same analysis is done for the constant mass case. It is also pointed out that our results are in agreement with those obtained in literature. Meanwhile, an analytic expression is obtained for the transmission resonance and it is observed that the expressions for bound states and resonances are equal for the energy values E = ±m.

Scattering of the Woods–Saxon potential in the Schrödinger equation

The scattering solutions of the one-dimensional Schrodinger equation for the Woods–Saxon potential are obtained within the position-dependent mass formalism. The wavefunctions, transmission and reflection coefficients are calculated in terms of Heuns function. These results are also studied in detail for the constant mass case.

Energy Density Associated with the Bianchi Type-II Space-Time

To calculate the total energy distribution (due to both matter and fields including gravitation) associated with locally rotationally symmetric (LRS) Bianchi type-II space-times. We use the Bergmann-Thomson energy-momentum complex in both general relativity and teleparallel gravity. We find that the energy density in these different gravitation theories is vanishing at all times. This result is the same as that obtained by one of the present authors who solved the problem of finding the energy-momentum in LRS Bianchi type-II by using the energy-momentum complexes of Einstein and Landau and Lifshitz. The results of this paper also are consistent with those given in the previous works of Cooperstock and Israelit,

GRAVITATIONAL ENERGY–MOMENTUM DENSITY IN BIANCHI TYPE II SPACE–TIMES

In this paper, using Einstein, Landau and Lifshitzs energy–momentum complexes both in general relativity and teleparallel gravity, we calculate the total energy distribution (due to matter and fields, including gravitation) associated with locally rotationally symmetric (LRS) Bianchi type II cosmological models. We show that energy densities in these different gravitation theories are the same, so they agree with each other. We obtain the result that the total energy is zero. This result agrees with previous works of Cooperstock and Israelit, Rosen, Johri et al., Banerjee and Sen, Vargas, Aydogdu and Salti. Moreover, our result supports the viewpoints of Albrow and Tryon.

Energy in the Schwarzschild-de Sitter Spacetime

The energy (due to matter and fields including gravitation) of the Schwarzschild-de Sitter spacetime is investigated by using the Møller energy-momentum definition in both general relativity and teleparallel gravity. We found the same energy distribution for a given metric in both of these different gravitation theories. It is also independent of the teleparallel dimensionless coupling constant, which means that it is valid in any teleparallel model. Our results sustain that (a) the importance of the energy-momentum definitions in the evaluation of the energy distribution of a given spacetime and (b) the viewpoint of Lessner that the Møller energy-momentum complex is a powerfifi concept of energy and momentum.