2,481 research outputs found
Accuracy of one-dimensional collision integral in the rigid spheres approximation
The accuracy of calculation of spectral line shapes in one-dimensional
approximation is studied analytically in several limiting cases for arbitrary
collision kernel and numerically in the rigid spheres model. It is shown that
the deviation of the line profile is maximal in the center of the line in case
of large perturber mass and intermediate values of collision frequency. For
moderate masses of buffer molecules the error of one-dimensional approximation
is found not to exceed 5%.Comment: LaTeX, 24 pages, 8 figure
Expanded Strings in the Background of NS5-branes via a M2-brane, a D2-brane and D0-branes
Classical configurations of a M2-brane, a D2-brane and D0-branes are
investigated in the background of an infinite array of M5-branes or NS5-branes.
On the M2-brane, we discuss three kinds of configurations, such as a sphere, a
cylinder and a torus-like one. These are stabilized by virtue of the background
fluxes of M5-branes. The torus-like M2-brane configuration has winding and
momentum numbers of 11th direction, and in terms of the type IIA superstring
theory, this corresponds to a torus-like D2-brane with electric and magnetic
fluxes on it. We also reproduce the same configuration from a non-abelian
Born-Infeld action for D0-branes. It will be a construction of closed strings
from D0-branes. An electric flux quantization condition on the D2-brane is also
discussed in terms of D0-branes.Comment: 33 pages, 6 figures, references and footnote added, confusing
expressions and introduction are improved, version to appear in JHE
Directed current due to broken time-space symmetry
We consider the classical dynamics of a particle in a one-dimensional
space-periodic potential U(X) = U(X+2\pi) under the influence of a
time-periodic space-homogeneous external field E(t)=E(t+T). If E(t) is neither
symmetric function of t nor antisymmetric under time shifts , an ensemble of trajectories with zero current at t=0 yields a nonzero
finite current as . We explain this effect using symmetry
considerations and perturbation theory. Finally we add dissipation (friction)
and demonstrate that the resulting set of attractors keeps the broken symmetry
property in the basins of attraction and leads to directed currents as well.Comment: 2 figure
Nature of the light scalar mesons
Despite the apparent simplicity of meson spectroscopy, light scalar mesons
cannot be accommodated in the usual structure. We study the
description of the scalar mesons below 2 GeV in terms of the mixing of a chiral
nonet of tetraquarks with conventional states. A strong
diquark-antidiquark component is found for several states. The consideration of
a glueball as dictated by quenched lattice QCD drives a coherent picture of the
isoscalar mesons.Comment: 14 pages, 1 figure, accepted for publication in Phys. Rev.
MICROSATELLITES-BASED EVALUATION OF THE PEAR CULTIVARS SELECTED FROM NIKITSKY BOTANICAL GARDENS GERMPLASM BY THEIR ECONOMICALLY VALUABLE CHARACTERISTICS
Mobilization and preservation of genetic sources of diversity of the cultivated pear varieties and their wild relatives is one of the main aspects of new cultivars breeding for modern intensive horticulture. The crucial matter during a new cultivar creation goes to the selection of parental pairs, which obtain a complex of positive features. The aim of this work is to study the Gene Fund collection of pear plantings from Nikitsky Botanical Gardens in accordance with the main economically important traits and to select the most valuable genotypes for using them in breeding programs as a starting material, as well as to conduct a DNA-fingerprinting and the analyses of genetic polymorphism of promising cultivars from the collection of pear with implementing of microsatellite analyses. As a result of long-term studies the following cultivars were selected in accordance with the complex of features promising for the breeding program: Gvardeiskaya Zimnyaya, Izuminka Kryma, Izumrudnaya, Kelmenchanka, Krymskaya Aromatnaya, Krymskaya Medovaya, Lazurnaya, Maria, Mriya, Nadezhda Stepi, Nezabudka, Novosadovskaya, Oreanda Kryma, Otechestvennaya, Tauschaya, Yakimovskaya. The samples of these cultivars were forwarded for genotyping. For the genetic polymorphism analyses of the studied cultivars, seven microsatellite DNA-markers – EMPc108, EMPc117, EMPc115, CH04e03 and CH01d09, CH01f07a, CH01d08 – grouped into 2 multiplex sets were used. The SSR-markers were significantly different according to their level of polymorphism – from 3 (CH04e03 marker) to 11 (EMPc115) alleles per a gene locus were revealed, the effective number of alleles varying from 1.37 to 4.65. Based on SSR-markers polymorphism analysis data, the rate of genetic similarity of the studied pear cultivars was estimated. This evaluation research helped estimate genetic relations inside the studied sample collection of genotypes. The SSR-fingerprints of the cultivars obtained will be used as a starting material for the creation of DNA-passports database of the “NBG – NSC” Gene Fund collection of pear cultivars
Transport of a Luttinger liquid in the presence of a time dependent impurity
We show that the macroscopic current and charge can be formulated as a
Quantum Mechanical zero mode problem. We find that the current is given by the
velocity operator of a particle restricted to move around a circle. As an
explicit example we investigate a Luttinger liquid of length which is
perturbed by a time dependent impurity. Using the statistical mechanics of zero
modes we computed the non-equilibrium current. In particular we show that in
the low temperature limit, , the zero mode method introduced here
becomes essential for computing the current
External voltage sources and Tunneling in quantum wires
We (re) consider in this paper the problem of tunneling through an impurity
in a quantum wire with arbitrary Luttinger interaction parameter. By combining
the integrable approach developed in the case of Quantum Hall edge states with
the introduction of radiative boundary conditions to describe the adiabatic
coupling to reservoirs, we are able to obtain the exact equilibrium and non
equilibrium current. One of the most striking features observed is the
appearance of negative differential conductances out of equilibrium in the
strongly interacting regime g <=.2. In spite of the various charging effects, a
remarkable form of duality is still observed.
New results on the computation of transport properties in integrable impurity
problems are gathered in appendices. In particular, we prove that the TBA
results satisfy a remarkable relation, originally derived using the Keldysh
formalism, between the order T^2 correction to the current out of equilibrium
and the second derivative of this current at T=0 with respect to the voltage.Comment: 16 pages, 7 figure
Exploration of Possible Quantum Gravity Effects with Neutrinos II: Lorentz Violation in Neutrino Propagation
It has been suggested that the interactions of energetic particles with the
foamy structure of space-time thought to be generated by quantum-gravitational
(QG) effects might violate Lorentz invariance, so that they do not propagate at
a universal speed of light. We consider the limits that may be set on a linear
or quadratic violation of Lorentz invariance in the propagation of energetic
neutrinos, v/c=[1 +- (E/M_\nuQG1)] or [1 +- (E/M_\nu QG2}^2], using data from
supernova explosions and the OPERA long-baseline neutrino experiment.Comment: 8 pages, 6 figures, proceedings for invited talk by A.Sakharov at
DISCRETE'08, Valencia, Spain; December 200
- …