341 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
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
Bose-Einstein condensation of magnons under incoherent pumping
Bose-Einstein condensation in a gas of magnons pumped by an incoherent
pumping source is experimentally studied at room temperature. We demonstrate
that the condensation can be achieved in a gas of bosons under conditions of
incoherent pumping. Moreover, we show the critical transition point is almost
independent of the frequency spectrum of the pumping source and is solely
determined by the density of magnons. The electromagnetic power radiated by the
magnon condensate was found to scale quadratically with the pumping power,
which is in accordance with the theory of Bose-Einstein condensation in magnon
gases
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
h-deformation of Gr(2)
The -deformation of functions on the Grassmann matrix group is
presented via a contraction of . As an interesting point, we have seen
that, in the case of the -deformation, both R-matrices of and
are the same
Quantum Mechanics on the h-deformed Quantum Plane
We find the covariant deformed Heisenberg algebra and the Laplace-Beltrami
operator on the extended -deformed quantum plane and solve the Schr\"odinger
equations explicitly for some physical systems on the quantum plane. In the
commutative limit the behaviour of a quantum particle on the quantum plane
becomes that of the quantum particle on the Poincar\'e half-plane, a surface of
constant negative Gaussian curvature. We show the bound state energy spectra
for particles under specific potentials depend explicitly on the deformation
parameter . Moreover, it is shown that bound states can survive on the
quantum plane in a limiting case where bound states on the Poincar\'e
half-plane disappear.Comment: 16pages, Latex2e, Abstract and section 4 have been revise
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