39,472 research outputs found
Spin-transfer torques in anti-ferromagnetic metals from first principles
In spite of the absence of a macroscopic magnetic moment, an anti-ferromagnet
is spin-polarized on an atomic scale. The electric current passing through a
conducting anti-ferromagnet is polarized as well, leading to spin-transfer
torques when the order parameter is textured, such as in anti-ferromagnetic
non-collinear spin valves and domain walls. We report a first principles study
on the electronic transport properties of anti-ferromagnetic systems. The
current-induced spin torques acting on the magnetic moments are comparable with
those in conventional ferromagnetic materials, leading to measurable angular
resistances and current-induced magnetization dynamics. In contrast to
ferromagnets, spin torques in anti-ferromagnets are very nonlocal. The torques
acting far away from the center of an anti-ferromagnetic domain wall should
facilitate current-induced domain wall motion.Comment: The paper has substantially been rewritten, 4 pages, 5 figure
Strong decays of heavy baryons in Bethe-Salpeter formalism
In this paper we study the properties of diquarks (composed of and/or
quarks) in the Bethe-Salpeter formalism under the covariant instantaneous
approximation. We calculate their BS wave functions and study their effective
interaction with the pion. Using the effective coupling constant among the
diquarks and the pion, in the heavy quark limit , we calculate
the decay widths of () in the BS formalism under the
covariant instantaneous approximation and then give predictions of the decay
widths .Comment: 41 pages, 1 figure, LaTex2e, typos correcte
Устроєві засади громадського судочинства й народна правосвідомість на українських землях у складі Великого Князівства Литовського
A general condition of inflationary cosmology on trans-Planckian physics
We consider a more general initial condition satisfying the minimal
uncertainty relationship. We calculate the power spectrum of a simple model in
inflationary cosmology. The results depend on perturbations generated below a
fundamental scale, e.g. the Planck scale.Comment: 7 pages, References adde
On graded polynomial identities with an antiautomorphism
AbstractLet G be a commutative monoid with cancellation and let R be a strongly G-graded associative algebra with finite G-grading and with antiautomorphism. Suppose that R satisfies a graded polynomial identity with antiautomorphism. We show that R is a PI algebra
Multi-mode entanglement of N harmonic oscillators coupled to a non-Markovian reservoir
Multi-mode entanglement is investigated in the system composed of coupled
identical harmonic oscillators interacting with a common environment. We treat
the problem very general by working with the Hamiltonian without the
rotating-wave approximation and by considering the environment as a
non-Markovian reservoir to the oscillators. We invoke an -mode unitary
transformation of the position and momentum operators and find that in the
transformed basis the system is represented by a set of independent harmonic
oscillators with only one of them coupled to the environment. Working in the
Wigner representation of the density operator, we find that the covariance
matrix has a block diagonal form that it can be expressed in terms of multiples
of and matrices. This simple property allows to treat
the problem to some extend analytically. We illustrate the advantage of working
in the transformed basis on a simple example of three harmonic oscillators and
find that the entanglement can persists for long times due to presence of
constants of motion for the covariance matrix elements. We find that, in
contrast to what one could expect, a strong damping of the oscillators leads to
a better stationary entanglement than in the case of a weak damping.Comment: 21 pages, 4 figure
Prostaglandin E2 Adds Bone to a Cancellous Bone Site with a Closed Growth Plate and Low Bone Turnover in Ovariectomized Rats
The objects of this study were to determine the responses of a cancellous bone site with a closed growth plate, (the distal tibial metaphysis (DTM), to ovariectomy (OVX) and OVX plus a prostaglandin E(2) treatment, and compare the site's response to previous findings reported for another site, the proximal tibial metaphysis (PTM). Thirty five 3-month old female Sprague-Dawley rats were divided into five groups; basal, sham OVX, and OVX+0, +1, or +6 mg PGE(2)/kg/d injected subcutaneously for 3 months and given double fluorescent labels before sacrifice. Cancellous bone histomorphometric analyses were performed on 20 micrometer thick undecalcified DTM sections. Similar to the PTM, the DTM showed age-related decreases in bone formation and increases in bone resorption, but it differed in that at 3 months POST OVX there was neither bone loss nor changes in formation endpoints. Giving 1 mg PGE(2)/kg/d to OVX rats prevented most age-related changes and maintained the bone formation histomorphometry near basal levels. Treating OVX rats with 6 mg PGE(2)/kd/d prevented age-related bone changes, added extra bone, and improved microanatomical structure by stimulating bone formation, without altering bone resportion. Futhermore, After PGE(2) admimnistration, the DTM, a cancellous bone site with a closed growth plate, increased bone formation more than did the cancellous bone in the PTM
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