7,053 research outputs found
Semiclassical Inequivalence of Polygonalized Billiards
Polygonalization of any smooth billiard boundary can be carried out in
several ways. We show here that the semiclassical description depends on the
polygonalization process and the results can be inequivalent. We also establish
that generalized tangent-polygons are closest to the corresponding smooth
billiard and for de Broglie wavelengths larger than the average length of the
edges, the two are semiclassically equivalent.Comment: revtex, 4 ps figure
Marketing concept stimulates economic development of our country
This research work outlines importance, factors of marketing concept and shows how the later escalates economic development of the country.Дане дослідження визначає роль, фактори маркетингової концепції та показує вплив на подальший економічний розвиток країни.Данное исследование определяет роль, факторы маркетинговой концепции и показывает влияние на дальнейшее экономическое развитие страны
Experimentally Constrained Molecular Relaxation: The Case of Glassy GeSe2
An ideal atomistic model of a disordered material should contradict no
experiments,and should also be consistent with accurate force fields (either
{\it ab initio}or empirical). We make significant progress toward jointly
satisfying {\it both} of these criteria using a hybrid reverse Monte Carlo
approach in conjunction with approximate first principles molecular dynamics.
We illustrate the method by studying the complex binary glassy material
g-GeSe. By constraining the model to agree with partial structure factors
and {\it ab initio} simulation, we obtain a 647-atom model in close agreement
with experiment, including the first sharp diffraction peak in the static
structure factor. We compute the electronic state densities and compare to
photoelectron spectroscopies. The approach is general and flexible.Comment: 6 pages, 4 figure
Modification of the Charge ordering in PrSrMnO Nanoparticles
Transport and magnetic properties have been studied in two sets of sol-gel
prepared PrSrMnO nanoparticles having average particle
size of 30 nm and 45 nm. Our measurements suggest that the formation of charge
ordered state is largely affected due to lowering of particle size, but the
ferromagnetic transition temperature () remains unaffected.Comment: Accepted in J. Appl. Phy
Low-energy quenching of positronium by helium
Very low-energy scattering of orthopositronium by helium has been
investigated for simultaneous study of elastic cross section and pick-off
quenching rate using a model exchange potential. The present calculational
scheme, while agrees with the measured cross section of Skalsey et al,
reproduces successfully the parameter ^ 1Z_{\makebox{eff}}, the effective
number of electrons per atom in a singlet state relative to the positron.
Together with the fact that this model potential also leads to an agreement
with measured medium energy cross sections of this system, this study seems to
resolve the long-standing discrepancy at low energies among different
theoretical calculations and experimental measurements.Comment: 4 latex pages, 3 postscript figure
The Effect of Different Foam Concentrations on Sperm Motility in Japanese Quail
A study was conducted to determine the effect of foam extract on sperm motility in the male Japanese quail (Coturnix coturnix japonica). Adult male quails (<12 weeks) of heavy body weight strain were housed in individual cages and divided into 5 groups according to the size of their cloacal glands. The data indicated that the size of the cloacal gland was positively correlated with the frequency of foam secretion and total foam production. One gram of freshly collected clean foam was mixed with 1.0 mL of normal saline and homogenized for 10 minutes. After centrifugation at 35 000 rpm, the supernatant was used as 100% foam extract. The extract was diluted to 1:40, 1:20, 1:10, and 1:4 with normal saline to produce 2.5, 5.0, 10, and 25% foam extracts, respectively. 5% foam extract enhanced sperm survival at room temperature (30°–35°C) for 2 to 3 hrs, whereas higher concentrations (10% and above) suppressed sperm motility. From this study, it may be concluded that foam secretion and quantity of foam are directly proportional to the size of the cloacal gland and that the foam enhances and prolongs sperm motility, in vitro at an optimum concentration of 5%
Zeta Function Zeros, Powers of Primes, and Quantum Chaos
We present a numerical study of Riemann's formula for the oscillating part of
the density of the primes and their powers. The formula is comprised of an
infinite series of oscillatory terms, one for each zero of the zeta function on
the critical line and was derived by Riemann in his paper on primes assuming
the Riemann hypothesis. We show that high resolution spectral lines can be
generated by the truncated series at all powers of primes and demonstrate
explicitly that the relative line intensities are correct. We then derive a
Gaussian sum rule for Riemann's formula. This is used to analyze the numerical
convergence of the truncated series. The connections to quantum chaos and
semiclassical physics are discussed
On the curvature of vortex moduli spaces
We use algebraic topology to investigate local curvature properties of the
moduli spaces of gauged vortices on a closed Riemann surface. After computing
the homotopy type of the universal cover of the moduli spaces (which are
symmetric powers of the surface), we prove that, for genus g>1, the holomorphic
bisectional curvature of the vortex metrics cannot always be nonnegative in the
multivortex case, and this property extends to all Kaehler metrics on certain
symmetric powers. Our result rules out an established and natural conjecture on
the geometry of the moduli spaces.Comment: 25 pages; final version, to appear in Math.
Level statistics and eigenfunctions of pseudointegrable systems: dependence on energy and genus number
We study the level statistics (second half moment and rigidity
) and the eigenfunctions of pseudointegrable systems with rough
boundaries of different genus numbers . We find that the levels form energy
intervals with a characteristic behavior of the level statistics and the
eigenfunctions in each interval. At low enough energies, the boundary roughness
is not resolved and accordingly, the eigenfunctions are quite regular functions
and the level statistics shows Poisson-like behavior. At higher energies, the
level statistics of most systems moves from Poisson-like towards Wigner-like
behavior with increasing . Investigating the wavefunctions, we find many
chaotic functions that can be described as a random superposition of regular
wavefunctions. The amplitude distribution of these chaotic functions
was found to be Gaussian with the typical value of the localization volume
. For systems with periodic boundaries we find
several additional energy regimes, where is relatively close to the
Poisson-limit. In these regimes, the eigenfunctions are either regular or
localized functions, where is close to the distribution of a sine or
cosine function in the first case and strongly peaked in the second case. Also
an interesting intermediate case between chaotic and localized eigenfunctions
appears
Robust transmission of non-Gaussian entanglement over optical fibers
We show how the entanglement in a wide range of continuous variable
non-Gaussian states can be preserved against decoherence for long-range quantum
communication through an optical fiber. We apply protection via
decoherence-free subspaces and quantum dynamical decoupling to this end. The
latter is implemented by inserting phase shifters at regular intervals inside the fiber, where is roughly the ratio of the speed of light
in the fiber to the bath high-frequency cutoff. Detailed estimates of relevant
parameters are provided using the boson-boson model of system-bath interaction
for silica fibers, and is found to be on the order of a millimeter.Comment: 9 pages, 2 figures, RevTeX4, submitted to PR
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