31 research outputs found
A QCD Sum Rule Approach to the Contribution to the Radiative Decay
QCD sum rules are used to calculate the contribution of short-distance
single-quark transition , to the amplitudes of the
hyperon radiative decay, . We re-evaluate the
Wilson coefficient of the effective operator responsible for this transition.
We obtain a branching ratio which is comparable to the unitarity limit.Comment: 15 pages, Revtex, 13 figures available as a uuencoded, gz-compressed
ps fil
New Longitudinal Waves in Electron-Positron-Ion Quantum Plasmas
A general quantum dispersion equation for electron-positron(hole)-ion quantum
plasmas is derived and studied for some interesting cases. In an
electron-positron degenerate Fermi gas, with or without the Madelung term, a
new type of zero sound waves are found. Whereas in an electron-hole plasmas a
new longitudinal quantum waves are revealed, which have no analogies in quantum
electron-ion plasmas. The excitation of these quantum waves by a low-density
monoenergetic straight electron beam is examined. Furthermore, the KdV equation
for novel quantum waves is derived and the contribution of the Madelung term in
the formation of the KdV solitons is discussed
Striped antiferromagnetic order and electronic properties of stoichiometric LiFeAs from first-principles calculations
We investigate the structural, electronic, and magnetic properties of
stoichiometric LiFeAs by using state-of-the-arts first-principles method. We
find the magnetic ground-state by comparing the total energies among all the
possible magnetic orders. Our calculated internal positions of Li and As are in
good agreement with experiment. Our results show that stoichiometric LiFeAs has
almost the same striped antiferromagnetic spin order as other FeAs-based parent
compounds and tetragonal FeSe do, and the experimental fact that no magnetic
phase transition has been observed at finite temperature is attributed to the
tiny inter-layer spin coupling
On the solutions of the Schrodinger equation with some molecular potentials: wave function ansatz
Making an ansatz to the wave function, the exact solutions of the %
-dimensional radial Schrodinger equation with some molecular potentials like
pseudoharmonic and modified Kratzer potentials are obtained. The restriction on
the parameters of the given potential, and are also given,
where depends on a linear combination of the angular momentum quantum
number and the spatial dimensions and is a parameter in
the ansatz to the wave function. On inserting D=3, we find that the bound state
eigensolutions recover their standard analytical forms in literature.Comment: 14 page
Lowest-Landau-level theory of the quantum Hall effect: the Fermi-liquid-like state
A theory for a Fermi-liquid-like state in a system of charged bosons at
filling factor one is developed, working in the lowest Landau level. The
approach is based on a representation of the problem as fermions with a system
of constraints, introduced by Pasquier and Haldane (unpublished). This makes
the system a gauge theory with gauge algebra W_infty. The low-energy theory is
analyzed based on Hartree-Fock and a corresponding conserving approximation.
This is shown to be equivalent to introducing a gauge field, which at long
wavelengths gives an infinite-coupling U(1) gauge theory, without a
Chern-Simons term. The system is compressible, and the Fermi-liquid properties
are similar, but not identical, to those in the previous U(1) Chern-Simons
fermion theory. The fermions in the theory are effectively neutral but carry a
dipole moment. The density-density response, longitudinal conductivity, and the
current density are considered explicitly.Comment: 32 pages, revtex multicol
A Phenomenological Analysis of Gluon Mass Effects in Inclusive Radiative Decays of the and $\Upsilon
The shapes of the inclusive photon spectra in the processes \Jp \to \gamma
X and \Up \to \gamma X have been analysed using all available experimental
data.
Relativistic, higher order QCD and gluon mass corrections were taken into
account in the fitted functions. Only on including the gluon mass corrections,
were consistent and acceptable fits obtained. Values of
GeV and GeV were found for the
effective gluon masses (corresponding to Born level diagrams) for the \Jp and
\Up respectively. The width ratios \Gamma(V \to {\rm hadrons})/\Gamma(V \to
\gamma+ {\rm hadrons}) V=\Jp, \Up were used to determine and . Values consistent with the current world
average were obtained only when gluon mass correction factors,
calculated using the fitted values of the effective gluon mass, were applied. A
gluon mass GeV, as suggested with these results, is consistent with
previous analytical theoretical calculations and independent phenomenological
estimates, as well as with a recent, more accurate, lattice calculation of the
gluon propagator in the infra-red region.Comment: 50 pages, 11 figures, 15 table
Expressões analíticas para a probabilidade de tunelamento em fenômeno de emissão por campo
A General Approach for the Exact Solution of the Schrodinger Equation
The Schr\"{o}dinger equation is solved exactly for some well known
potentials. Solutions are obtained reducing the Schr\"{o}dinger equation into a
second order differential equation by using an appropriate coordinate
transformation. The Nikiforov-Uvarov method is used in the calculations to get
energy eigenvalues and the corresponding wave functions.Comment: 20 page