2,802 research outputs found
A quantum exactly solvable non-linear oscillator related with the isotonic oscillator
A nonpolynomial one-dimensional quantum potential representing an oscillator,
that can be considered as placed in the middle between the harmonic oscillator
and the isotonic oscillator (harmonic oscillator with a centripetal barrier),
is studied. First the general case, that depends of a parameter , is
considered and then a particular case is studied with great detail. It is
proven that it is Schr\"odinger solvable and then the wave functions
and the energies of the bound states are explicitly obtained. Finally it
is proven that the solutions determine a family of orthogonal polynomials
related with the Hermite polynomials and such that: (i) Every
is a linear combination of three Hermite polynomials, and (ii)
They are orthogonal with respect to a new measure obtained by modifying the
classic Hermite measure.Comment: 11 pages, 11 figure
Semiclassical wave equation and exactness of the WKB method
The exactness of the semiclassical method for three-dimensional problems in
quantum mechanics is analyzed. The wave equation appropriate in the
quasiclassical region is derived. It is shown that application of the standard
leading-order WKB quantization condition to this equation reproduces exact
energy eigenvalues for all solvable spherically symmetric potentials.Comment: 13 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
Thermal Radiation from Au + Au Collisions at \sqrt{s} = 200 GEV/A Energy
The transverse momentum distribution of the direct photons measured by the
PHENIX collaboration in collisions at GeV/A has been
analyzed. It has been shown that the data can be reproduced reasonably well
assuming a deconfined state of thermalized quarks and gluons with initial
temperature more than the transition temperature for deconfinement inferred
from lattice QCD. The value of the initial temperature depends on the equation
of state of the evolving matter. The sensitivities of the results on various
input parameters have been studied. The effects of the modifications of
hadronic properties at non-zero temperature have been discussed.Comment: minor modifications in the text, accepted for publicatio
The systematic study of the influence of neutron excess on the fusion cross sections using different proximity-type potentials
Using different types of proximity potentials, we have examined the trend of
variations of barrier characteristics (barrier height and its position) as well
as fusion cross sections for 50 isotopic systems including various collisions
of C, O, Mg, Si, S, Ca, Ar, Ti and Ni nuclei with condition
for compound systems. The results of our studies reveal that the relationships
between increase of barrier positions and decrease of barrier heights are both
linear with increase of ratio. Moreover, fusion cross sections also
enhance linearly with increase of this ratio.Comment: 28 pages, 7 figures, 5 Table
One-dimensional fermions with incommensuration
We study the spectrum of fermions hopping on a chain with a weak
incommensuration close to dimerization; both q, the deviation of the wave
number from pi, and delta, the strength of the incommensuration, are small. For
free fermions, we use a continuum Dirac theory to show that there are an
infinite number of bands which meet at zero energy as q approaches zero. In the
limit that the ratio q/ \delta --> 0, the number of states lying inside the q=0
gap is nonzero and equal to 2 \delta /\pi^2. Thus the limit q --> 0 differs
from q=0; this can be seen clearly in the behavior of the specific heat at low
temperature. For interacting fermions or the XXZ spin-1/2 chain close to
dimerization, we use bosonization to argue that similar results hold; as q -->
0, we find a nontrivial density of states near zero energy. However, the limit
q --> 0 and q=0 give the same results near commensurate wave numbers which are
different from pi. We apply our results to the Azbel-Hofstadter problem of
electrons hopping on a two-dimensional lattice in the presence of a magnetic
field. Finally, we discuss the complete energy spectrum of noninteracting
fermions with incommensurate hopping by going up to higher orders in delta.Comment: Revtex, 23 pages including 7 epsf figures; this is a greatly expanded
version of cond-mat/981133
Resonant enhancement of the zero-phonon emission from a color center in a diamond cavity
We demonstrate coupling of the zero-phonon line of individual
nitrogen-vacancy centers and the modes of microring resonators fabricated in
single-crystal diamond. A zero-phonon line enhancement exceeding ten-fold is
estimated from lifetime measurements at cryogenic temperatures. The devices are
fabricated using standard semiconductor techniques and off-the-shelf materials,
thus enabling integrated diamond photonics.Comment: 5 pages, 4 figure
Tensor Coupling and Vector Mesons in Dense Nuclear Matter
The effects of magnetic interaction between vector mesons and nucleons on the
propagation (mass and width) of the -meson in particular moving through
very dense nuclear matter is studied and the modifications, qualitative and
quantitative, due to the relevant collective modes (zero-sound and plasma
frequencies) of the medium discussed. It is shown that the -mesons
produced in high-energy nuclear collisions will be longitudinally polarized in
the region of sufficiently dense nuclear matter, in the presence of such an
interaction.Comment: Plain Latex file. Three figures, not appended, may be obtained on
request to [email protected]
Approximate solution of the Duffin-Kemmer-Petiau equation for a vector Yukawa potential with arbitrary total angular momenta
The usual approximation scheme is used to study the solution of the
Duffin-Kemmer-Petiau (DKP) equation for a vector Yukawa potential in the
framework of the parametric Nikiforov-Uvarov (NU) method. The approximate
energy eigenvalue equation and the corresponding wave function spinor
components are calculated for arbitrary total angular momentum in closed form.
Further, the approximate energy equation and wave function spinor components
are also given for case. A set of parameter values is used to obtain the
numerical values for the energy states with various values of quantum levelsComment: 17 pages; Communications in Theoretical Physics (2012). arXiv admin
note: substantial text overlap with arXiv:1205.0938, and with
arXiv:quant-ph/0410159 by other author
Study of in-medium meson properties in Ap, pA and AA collisions
We propose to investigate the in-medium properties of vector mesons
at the normal nuclear density in Ap(pA) collisions and at higher density in AA
collisions at the ITEP accelerator facility TWAC. Using of the inverse Ap
kinematics will permit us to study the meson production in a wide
momentum interval included the not yet explored range of small meson momenta
relative to the projectile nuclei where the mass modification effect in nuclear
matter is expected to be the strongest. Momentum dependence of the in-medium
meson width will be studied in the traditional pA kinematics. We
intend to use the electromagnetic calorimeter for reconstruction of the
meson invariant mass by detecting photons from the decay. The model calculations and simulations with
RQMD generator show feasibility of the proposed experiment. Available now
intensity of the ion beams provides a possibility to collect large statistics
and make decisive conclusion about the meson properties at density of
normal nuclei. At the second stage of the investigation the meson
properties will be studied in AA collisions at higher density. Interpretation
of these measurements will be based on the results obtained in Ap(pA)
interactions. Further investigation of the in-medium properties of light
unflavored and charmed mesons can be performed at ITEP and at GSI(FAIR) where
higher ion energies will be accessible in near future.Comment: 26 pages, 10 figures, 2 table
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