95,495 research outputs found
A Generalization of Mathieu Subspaces to Modules of Associative Algebras
We first propose a generalization of the notion of Mathieu subspaces of
associative algebras , which was introduced recently in [Z4] and
[Z6], to -modules . The newly introduced notion in a
certain sense also generalizes the notion of submodules. Related with this new
notion, we also introduce the sets and of stable elements
and quasi-stable elements, respectively, for all -subspaces of -modules , where is the base ring of . We then
prove some general properties of the sets and .
Furthermore, examples from certain modules of the quasi-stable algebras [Z6],
matrix algebras over fields and polynomial algebras are also studied.Comment: A new case has been added; some mistakes and misprints have been
corrected. Latex, 31 page
NLTE study of scandium in the Sun
We investigate the formation of neutral and singly ionized scandium lines in
the solar photospheres. The research is aimed derive solar (Sc) values for scandium lines, which will later be used in
differential abundance analyses of metal-poor stars. Extensive statistical
equilibrium calculations were carried out for a model atom, which comprises 92
terms for \ion{Sc}{i} and 79 for \ion{Sc}{ii}. Photoionization cross-sections
are assumed to be hydrogenic. Synthetic line profiles calculated from the level
populations according to the NLTE departure coefficients were compared with the
observed solar spectral atlas. Hyperfine structure (HFS) broadening is taken
into account. The statistical equilibrium of scandium is dominated by a strong
underpopulation of \ion{Sc}{i} caused by missing strong lines. It is nearly
unaffected by the variation in interaction parameters and only marginally
sensitive to the choice of the solar atmospheric model. Abundance
determinations using the ODF model lead to a solar Sc abundance of between
and 3.13, depending on the choice of values.
The long known difference between photospheric and meteoritic scandium
abundances is confirmed for the experimental -values.Comment: 10 pages, 6 figures, A&A accepte
Extracting and Stabilizing the Unstable State of Hysteresis Loop
A novel perturbation method for the stabilization of unstable intermediate
states of hysteresis loop (i.e. S-shaped curve) is proposed. This method only
needs output signals of the system to construct the perturbation form without
delay-coordinate embedding technique, it is more practical for real-world
systems. Stabilizing and tracking the unstable intermediate branch are
demonstrated through the examples of a bistable laser system and delay feedback
system. All the numerical results are obtained by simulating each of the real
experimential conditions.Comment: 6 pages, REVTEX, 4 ps figure
A New Kind of Uniformly Accelerated Reference Frames
A new kind of uniformly accelerated reference frames with a line-element
different from the M{\o}ller and Rindler ones is presented, in which every
observer at consts. has the same constant acceleration. The laws of
mechanics are checked in the new kind of frames. Its thermal property is
studied. The comparison with the M{\o}ller and Rindler uniform accelerated
reference frames is also made.Comment: 10 pages, 2 figures. to appear in Int. J. Mod. Phys.
Electrical transport in the ferromagnetic state of manganites: Small-polaron metallic conduction at low temperatures
We report measurements of the resistivity in the ferromagnetic state of
epitaxial thin films of La_{1-x}Ca_{x}MnO_{3} and the low temperature specific
heat of a polycrystalline La_{0.8}Ca_{0.2}MnO_{3}. The resistivity below 100 K
can be well fitted by \rho - \rho_{o} = E \omega_{s}/sinh^{2}(\hbar
\omega_{s}/2k_{B}T) with \hbar \omega_{s}/k_{B} \simeq 100 K and E being a
constant. Such behavior is consistent with small-polaron coherent motion which
involves a relaxation due to a soft optical phonon mode. The specific heat data
also suggest the existence of such a phonon mode. The present results thus
provide evidence for small-polaron metallic conduction in the ferromagnetic
state of manganites.Comment: 4 pages, 4 figures, submitted to PR
Self-similarity in a system with short-time delayed feedback
Using the Poincar\'{e} section technique, we study in detail the dynamical
behaviors of delay differential system and find a new type of solutions
in short-time delay feedback. Our numerical results remind us to deny the
opinion that there are no complex phenomena in short-time delay case. Many
similarities between foundamental solution and the new type of solutions are
found. We demonstrate that the scales of increase with exponential growth
via in the direction of , while decrease with exponential decays in
the direction of or delay time .Comment: 4 pages, REVTEX, 4 ps figures, to be published in Phys. Lett.
Self-consistent models of triaxial galaxies in MOND gravity
The Bekenstein-Milgrom gravity theory with a modified Poisson equation is
tested here for the existence of triaxial equilibrium solutions. Using the
non-negative least square method, we show that self-consistent triaxial
galaxies exist for baryonic models with a mild density cusp . Self-consistency is achieved for a wide range of central
concentrations, , representing
low-to-high surface brightness galaxies. Our results demonstrate for the first
time that the orbit superposition technique is fruitful for constructing galaxy
models beyond Newtonian gravity, and triaxial cuspy galaxies might exist
without the help of Cold dark Matter.Comment: 19 pages, 1 table, 7 figures, Accepted for publication in Ap
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