1,055 research outputs found
Calculation of francium hyperfine anomaly
The Dirac-Hartree-Fock plus many-body perturbation theory (DHF+MBPT) method
has been used to calculate hyperfine structure constants for Fr. Calculated
hyperfine structure anomaly for hydrogen-like ion has been shown to be in good
agreement with analytical expressions. It has been shown that the ratio of the
anomalies for and states is weakly dependent on the principal
quantum number. Finally, we estimate Bohr--Weisskopf corrections for several Fr
isotopes. Our results may be used to improve experimental accuracy for the
nuclear factors of short-lived isotopes.Comment: 5 pages, 3 tables, 2 figures. arXiv admin note: text overlap with
arXiv:1703.1004
Gauge theory solitons on noncommutative cylinder
We generalize to noncommutative cylinder the solution generation technique,
originally suggested for gauge theories on noncommutative plane. For this
purpose we construct partial isometry operators and complete set of orthogonal
projectors in the algebra of the cylinder, and an isomorphism between the free
module and its direct sum with the Fock module on the cylinder. We construct
explicitly the gauge theory soliton and evaluate the spectrum of perturbations
about this soliton.Comment: References added; to appear in Theor.Math.Phy
Magnetic anisotropy in strained manganite films and bicrystal junctions
Transport and magnetic properties of LSMO manganite thin films and bicrystal
junctions were investigated. Manganite films were epitaxially grown on STO,
LAO, NGO and LSAT substrates and their magnetic anisotropy were determined by
two techniques of magnetic resonance spectroscopy. Compare with cubic
substrates a small (about 0.3 persentage), the anisotropy of the orthorhombic
NGO substrate leads to a uniaxial anisotropy of the magnetic properties of the
films in the plane of the substrate. Samples with different tilt of
crystallographic basal planes of manganite as well as bicrystal junctions with
rotation of the crystallographic axes (RB - junction) and with tilting of basal
planes (TB - junction) were investigated. It was found that on vicinal NGO
substrates the value of magnetic anisotropy could be varied by changing the
substrate inclination angle from 0 to 25 degrees. Measurement of magnetic
anisotropy of manganite bicrystal junction demonstrated the presence of two
ferromagnetically ordered spin subsystems for both types of bicrystal
boundaries RB and TB. The magnitude of the magnetoresistance for TB - junctions
increased with decreasing temperature and with the misorientation angle even
misorientation of easy axes in the parts of junction does not change. Analysis
of the voltage dependencies of bicrystal junction conductivity show that the
low value of the magnetoresistance for the LSMO bicrystal junctions can be
caused by two scattering mechanisms with the spin- flip of spin - polarized
carriers due to the strong electron - electron interactions in a disordered
layer at the bicrystal boundary at low temperatures and the spin-flip by anti
ferromagnetic magnons at high temperatures.Comment: 26 pages, 10 figure
Differential Calculus on -Deformed Light-Cone
We propose the ``short'' version of q-deformed differential calculus on the
light-cone using twistor representation. The commutation relations between
coordinates and momenta are obtained. The quasi-classical limit introduced
gives an exact shape of the off-shell shifting.Comment: 11 pages, Standard LaTeX 2.0
The Bohr-Weisskopf effect in the potassium isotopes
The magnetic hyperfine structure constants have been calculated for low-lying
levels in neutral potassium atom taking into account the Bohr--Weisskopf (BW)
and Breit--Rosenthal (BR) effects. According to our results the
state of K~I is free from both BR and BW corrections on the level of the
current theoretical uncertainties. Using this finding and the measured values
of the constants, we corrected the nuclear magnetic moments for
several short-lived potassium isotopes. The BW correction is represented as a
product of atomic and nuclear factors. We calculated the atomic factor for the
ground state of K I, which allowed us to extract nuclear factors for potassium
isotopes from the experimental data. In this way the
application range of the single-particle nuclear model for nuclear-factor
calculation in these isotopes has been clarified
On the Hopf algebras generated by the Yang-Baxter R-matrices
We reformulate the method recently proposed for constructing quasitriangular
Hopf algebras of the quantum-double type from the R-matrices obeying the
Yang-Baxter equations. Underlying algebraic structures of the method are
elucidated and an illustration of its facilities is given. The latter produces
an example of a new quasitriangular Hopf algebra. The corresponding universal
R-matrix is presented as a formal power series.Comment: 10 page
The Ginzburg-Landau model of Bose-Einstein condensation of magnons
We introduce a system of phenomenological equations for Bose-Einstein
condensates of magnons in the one-dimensional setting. The nonlinearly coupled
equations, written for amplitudes of the right-and left-traveling waves,
combine basic features of the Gross-Pitaevskii and complex Ginzburg-Landau
models. They include localized source terms, to represent the microwave
magnon-pumping field. With the source represented by the -functions,
we find analytical solutions for symmetric localized states of the magnon
condensates. We also predict the existence of asymmetric states with unequal
amplitudes of the two components. Numerical simulations demonstrate that all
analytically found solutions are stable. With the -function terms
replaced by broader sources, the simulations reveal a transition from the
single-peak stationary symmetric states to multi-peak ones, generated by the
modulational instability of extended nonlinear-wave patterns. In the
simulations, symmetric initial conditions always converge to symmetric
stationary patterns. On the other hand, asymmetric inputs may generate
nonstationary asymmetric localized solutions, in the form of traveling or
standing waves. Comparison with experimental results demonstrates that the
phenomenological equations provide for a reasonably good model for the
description of the spatiotemporal dynamics of magnon condensates.Comment: Physical Review B, in pres
- …