6,669 research outputs found
Bound states of the Klein-Gordon equation for vector and scalar general Hulthen-type potentials in D-dimension
We solve the Klein-Gordon equation in any -dimension for the scalar and
vector general Hulth\'{e}n-type potentials with any by using an
approximation scheme for the centrifugal potential. Nikiforov-Uvarov method is
used in the calculations. We obtain the bound state energy eigenvalues and the
corresponding eigenfunctions of spin-zero particles in terms of Jacobi
polynomials. The eigenfunctions are physical and the energy eigenvalues are in
good agreement with those results obtained by other methods for D=1 and 3
dimensions. Our results are valid for value when and for any
value when and D=1 or 3. The % -wave () binding energies for
a particle of rest mass are calculated for the three lower-lying
states using pure vector and pure scalar potentials.Comment: 25 page
Any l-state improved quasi-exact analytical solutions of the spatially dependent mass Klein-Gordon equation for the scalar and vector Hulthen potentials
We present a new approximation scheme for the centrifugal term to obtain a
quasi-exact analytical bound state solutions within the framework of the
position-dependent effective mass radial Klein-Gordon equation with the scalar
and vector Hulth\'{e}n potentials in any arbitrary dimension and orbital
angular momentum quantum numbers The Nikiforov-Uvarov (NU) method is used
in the calculations. The relativistic real energy levels and corresponding
eigenfunctions for the bound states with different screening parameters have
been given in a closed form. It is found that the solutions in the case of
constant mass and in the case of s-wave () are identical with the ones
obtained in literature.Comment: 25 pages, 1 figur
Exact Klein-Gordon equation with spatially-dependent masses for unequal scalar-vector Coulomb-like potentials
We study the effect of spatially dependent mass functions over the solution
of the Klein-Gordon equation in the (3+1)-dimensions for spinless bosonic
particles where the mixed scalar-vector Coulomb-like field potentials and
masses are directly proportional and inversely proportional to the distance
from force center. The exact bound state energy eigenvalues and the
corresponding wave functions of the Klein-Gordon equation for mixed
scalar-vector and pure scalar Coulomb-like field potentials are obtained by
means of the Nikiforov-Uvarov (NU) method. The energy spectrum is discussed for
different scalar-vector potential mixing cases and also for constant mass case.Comment: 17 pages; to be published in European Journal of Physics A (2009
Discrete Breathers
Nonlinear classical Hamiltonian lattices exhibit generic solutions in the
form of discrete breathers. These solutions are time-periodic and (typically
exponentially) localized in space. The lattices exhibit discrete translational
symmetry. Discrete breathers are not confined to certain lattice dimensions.
Necessary ingredients for their occurence are the existence of upper bounds on
the phonon spectrum (of small fluctuations around the groundstate) of the
system as well as the nonlinearity in the differential equations. We will
present existence proofs, formulate necessary existence conditions, and discuss
structural stability of discrete breathers. The following results will be also
discussed: the creation of breathers through tangent bifurcation of band edge
plane waves; dynamical stability; details of the spatial decay; numerical
methods of obtaining breathers; interaction of breathers with phonons and
electrons; movability; influence of the lattice dimension on discrete breather
properties; quantum lattices - quantum breathers. Finally we will formulate a
new conceptual aproach capable of predicting whether discrete breather exist
for a given system or not, without actually solving for the breather. We
discuss potential applications in lattice dynamics of solids (especially
molecular crystals), selective bond excitations in large molecules, dynamical
properties of coupled arrays of Josephson junctions, and localization of
electromagnetic waves in photonic crystals with nonlinear response.Comment: 62 pages, LaTeX, 14 ps figures. Physics Reports, to be published; see
also at http://www.mpipks-dresden.mpg.de/~flach/html/preprints.htm
Solution of Effective-Mass Dirac Equation with Scalar-Vector and Pseudoscalar Terms for Generalized Hulth\'en Potential
We find the exact bound-state solutions and normalization constant for the
Dirac equation with scalar-vector-pseudoscalar interaction terms for the
generalized Hulth\'{e}n potential in the case where we have a particular mass
function . We also search the solutions for the constant mass where the
obtained results correspond to the ones when the Dirac equation has spin and
pseudospin symmetry, respectively. After giving the obtained results for the
non-relativistic case, we search then the energy spectra and corresponding
upper and lower components of Dirac spinor for the case of -symmetric forms
of the present potential.Comment: 21 pages, 1 Tabl
Evolution of near extremal black holes
Near extreme black holes can lose their charge and decay by the emission of
massive BPS charged particles. We calculate the greybody factors for low energy
charged and neutral scalar emission from four and five dimensional near
extremal Reissner-Nordstrom black holes. We use the corresponding emission
rates to obtain ratios of the rates of loss of excess energy by charged and
neutral emission, which are moduli independent, depending only on the integral
charges and the horizon potentials. We consider scattering experiments, finding
that evolution towards a state in which the integral charges are equal is
favoured, but neutral emission will dominate the decay back to extremality
except when one charge is much greater than the others. The implications of our
results for the agreement between black hole and D-brane emission rates and for
the information loss puzzle are then discussed.Comment: 25 pages, RevTe
Solutions of the spatially-dependent mass Dirac equation with the spin and pseudo-spin symmetry for the Coulomb-like potential
We study the effect of spatially dependent mass function over the solution of
the Dirac equation with the Coulomb potential in the (3+1)-dimensions for any
arbitrary spin-orbit state In the framework of the spin and
pseudospin symmetry concept, the analytic bound state energy eigenvalues and
the corresponding upper and lower two-component spinors of the two Dirac
particles are obtained by means of the Nikiforov-Uvarov method, in closed form.
This physical choice of the mass function leads to an exact analytical solution
for the pseudospin part of the Dirac equation. The special cases ( i.e., s-wave) the constant mass and the
non-relativistic limits are briefly investigated.Comment: 24 page
- …