1,128 research outputs found
Lagrange-Fedosov Nonholonomic Manifolds
We outline an unified approach to geometrization of Lagrange mechanics,
Finsler geometry and geometric methods of constructing exact solutions with
generic off-diagonal terms and nonholonomic variables in gravity theories. Such
geometries with induced almost symplectic structure are modelled on
nonholonomic manifolds provided with nonintegrable distributions defining
nonlinear connections. We introduce the concept of Lagrange-Fedosov spaces and
Fedosov nonholonomic manifolds provided with almost symplectic connection
adapted to the nonlinear connection structure.
We investigate the main properties of generalized Fedosov nonholonomic
manifolds and analyze exact solutions defining almost symplectic Einstein
spaces.Comment: latex2e, v3, published variant, with new S.V. affiliatio
Deformation Quantization of Almost Kahler Models and Lagrange-Finsler Spaces
Finsler and Lagrange spaces can be equivalently represented as almost Kahler
manifolds enabled with a metric compatible canonical distinguished connection
structure generalizing the Levi Civita connection. The goal of this paper is to
perform a natural Fedosov-type deformation quantization of such geometries. All
constructions are canonically derived for regular Lagrangians and/or
fundamental Finsler functions on tangent bundles.Comment: the latex 2e variant of the manuscript accepted for JMP, 11pt, 23
page
Parietal defects. Laparoscopic aproach
Spitalul Elias, București, România, Al XI-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova și cea de-a XXXIII-a Reuniune a Chirurgilor din Moldova „Iacomi-Răzeșu” 27-30 septembrie 2011Experiența clinicii țn defectele parietale abdominale prin abord laparoscopic.Clinic experience in abdominal parieteal defects with laparoscopic aproach
Al-Substitution Effects on Physical Properties of the Colossal Magnetoresistance Compouns La0.67ca0.33mno3
We present a detailed study of the polycrystalline perovskite manganites
La0.67Ca0.33AlxMn1-xO3 (x = 0, 0.1, 0.15, 0.5) at low temperatures and high
magnetic fields, including electrical resistance, magnetization, ac
susceptibility. The static magnetic susceptibility was also measured up to 1000
K. All the samples show colossal magnetoresistance behavior and the Curie
temperatures decrease with Al doping. The data suggest the presence of
correlated magnetic clusters near by the ferromagnetic transition. This appears
to be a consequence of the structural and magnetic disorder created by the
random distribution of Al atoms.Comment: 13 pages including 5 figure
On Generators of the Hardy and the Bergman Spaces
A function which is analytic and bounded in the Unit disk is called a
generator for the Hardy space or the Bergman space if polynomials in that
function are dense in the corresponding space. We characterize generators in
terms of sub-spaces which are invariant under multiplication by the generator
and also invariant under multiplication by z, and study wandering properties of
such sub-spaces. Density of bounded analytic functions in the sub-spaces of the
Hardy space which are invariant under multiplication by the generator is also
investigated.Comment: 9 page
Nonholonomic Ricci Flows: II. Evolution Equations and Dynamics
This is the second paper in a series of works devoted to nonholonomic Ricci
flows. By imposing non-integrable (nonholonomic) constraints on the Ricci flows
of Riemannian metrics we can model mutual transforms of generalized
Finsler-Lagrange and Riemann geometries. We verify some assertions made in the
first partner paper and develop a formal scheme in which the geometric
constructions with Ricci flow evolution are elaborated for canonical nonlinear
and linear connection structures. This scheme is applied to a study of
Hamilton's Ricci flows on nonholonomic manifolds and related Einstein spaces
and Ricci solitons. The nonholonomic evolution equations are derived from
Perelman's functionals which are redefined in such a form that can be adapted
to the nonlinear connection structure. Next, the statistical analogy for
nonholonomic Ricci flows is formulated and the corresponding thermodynamical
expressions are found for compact configurations. Finally, we analyze two
physical applications: the nonholonomic Ricci flows associated to evolution
models for solitonic pp-wave solutions of Einstein equations, and compute the
Perelman's entropy for regular Lagrange and analogous gravitational systems.Comment: v2 41 pages, latex2e, 11pt, the variant accepted by J. Math. Phys.
with former section 2 eliminated, a new section 5 with applications in
gravity and geometric mechanics, and modified introduction, conclusion and
new reference
The nature of domain walls in ultrathin ferromagnets revealed by scanning nanomagnetometry
The recent observation of current-induced domain wall (DW) motion with large
velocity in ultrathin magnetic wires has opened new opportunities for
spintronic devices. However, there is still no consensus on the underlying
mechanisms of DW motion. Key to this debate is the DW structure, which can be
of Bloch or N\'eel type, and dramatically affects the efficiency of the
different proposed mechanisms. To date, most experiments aiming to address this
question have relied on deducing the DW structure and chirality from its motion
under additional in-plane applied fields, which is indirect and involves strong
assumptions on its dynamics. Here we introduce a general method enabling
direct, in situ, determination of the DW structure in ultrathin ferromagnets.
It relies on local measurements of the stray field distribution above the DW
using a scanning nanomagnetometer based on the Nitrogen-Vacancy defect in
diamond. We first apply the method to a Ta/Co40Fe40B20(1 nm)/MgO magnetic wire
and find clear signature of pure Bloch DWs. In contrast, we observe left-handed
N\'eel DWs in a Pt/Co(0.6 nm)/AlOx wire, providing direct evidence for the
presence of a sizable Dzyaloshinskii-Moriya interaction (DMI) at the Pt/Co
interface. This method offers a new path for exploring interfacial DMI in
ultrathin ferromagnets and elucidating the physics of DW motion under current.Comment: Main text and Supplementary Information, 33 pages and 12 figure
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