Paramagnetic Meissner effect in superconductors from self-consistent solutions of Ginzburg-Landau equations

The paramagnetic Meissner effect (PME) is observed in small superconducting samples, and a number of controversial explanations of this effect are proposed, but there is as yet no clear understanding of its nature. In the present paper PME is considered on the base of the Ginzburg-Landau theory (GL). The one-dimensional solutions are obtained in a model case of a long superconducting cylinder for different cylinder radii R, the GL-parameters \kappa and vorticities m. Acording to GL-theory, PME is caused by the presence of vortices inside the sample. The superconducting current flows around the vortex to screeen the vortex own field from the bulk of the sample. Another current flows at the boundary to screen the external field H from entering the sample. These screening currents flow in opposite directions and contribute with opposite signs to the total magnetic moment (or magnetization) of the sample. Depending on H, the total magnetization M may be either negative (diamagnetism), or positive (paramagnetism). A very complicated saw-like dependence M(H) (and other characteristics), which are obtained on the base of self-consistent solutions of the GL-equations, are discussed.Comment: 6 pages, 5 figures, RevTex, submitted to Phys. Rev.

Anomalies of Density, Stresses, and the Gravitational Field in the Interior of Mars

We determined the possible compensation depths for relief harmonics of different degrees and orders. The relief is shown to be completely compensated within the depth range of 0 to 1400 km. The lateral distributions of compensation masses are determined at these depths and the maps are constructed. The possible nonisostatic vertical stresses in the crust and mantle of Mars are estimated to be 64 MPa in compression and 20 MPa in tension. The relief anomalies of the Tharsis volcanic plateau and symmetric feature in the eastern hemisphere could have arisen and been maintained dynamically due to two plumes in the mantle substance that are enriched with fluids. The plumes that originate at the core of Mars can arise and be maintained by the anomalies of the inner gravitational field achieving +800 mGal in the region of plume formation, - 1200 mGal above the lower mantle-core transition layer, and -1400 mGal at the crust.Comment: 9 pages, 5 figure

The 2013 February 17 sunquake in the context of the active region's magnetic field configuration

© 2017. The American Astronomical Society. All rights reserved. Sunquakes are created by the hydrodynamic response of the lower atmosphere to a sudden deposition of energy and momentum. In this study, we investigate a sunquake that occurred in NOAA active region 11675 on 2013 February 17. Observations of the corona, chromosphere, and photosphere are brought together for the first time with a nonlinear force-free model of the active region's magnetic field in order to probe the magnetic environment in which the sunquake was initiated. We find that the sunquake was associated with the destabilization of a flux rope and an associated M-class GOES flare. Active region 11675 was in its emergence phase at the time of the sunquake and photospheric motions caused by the emergence heavily modified the flux rope and its associated quasi-separatrix layers, eventually triggering the flux rope's instability. The flux rope was surrounded by an extended envelope of field lines rooted in a small area at the approximate position of the sunquake. We argue that the configuration of the envelope, by interacting with the expanding flux rope, created a “magnetic lens” that may have focussed energy on one particular location of the photosphere, creating the necessary conditions for the initiation of the sunquake

Mathematical model of the starter system for a three-stage synchronous generator with a damping cage

В данной статье рассматривается математическая модель стартерной системы для газотурбинных двигателей. Модель исследуемого трехкаскадного синхронного генератора была построена в системе d-q-координат. Полученная модель позволяет сконфигурировать параметры машины в широком диапазоне, а также получить информацию о токах и напряжениях основных электрических узлов машины. Математическое моделирование показало эффективность полученной модели и адекватность предложенного алгоритма электростартерного запуска синхронной машины.This paper, considers a mathematical model the starter system for gas turbine engines. Model of the investigated three-stage synchronous generator has been built in the dq-coordinates. The obtained model allows one to configure the machine parameters in a wide range, as well as receive information about currents and voltages major electrical components of the machine. Mathematical modeling shown efficiency of the resulting model and adequacy of the proposed algorithms electric starter mode synchronous machine

High Energy Neutrinos and Photons from Curvature Pions in Magnetars

We discuss the relevance of the curvature radiation of pions in strongly magnetized pulsars or magnetars, and their implications for the production of TeV energy neutrinos detectable by cubic kilometer scale detectors, as well as high energy photons.Comment: 19 pages, 4 figures, to appear in JCA

Supergroup approach to the Hubbard model

Based on the revealed hidden supergroup structure, we develop a new approach to the Hubbard model. We reveal a relation of even Hubbard operators to the spinor representation of the generators of the rotation group of four-dimensional spaces. We propose a procedure for constructing a matrix representation of translation generators, yielding a curved space on which dynamic superfields are defined. We construct a new deformed nonlinear superalgebra for the regime of spinless Hubbard model fermions in the case of large on-site repulsion and evaluate the effective functional for spinless fermions.Comment: 17 pages, Theoretical and Mathematical Physics, V.166, n.2, p.209-222,201

Electron-positron pair production in the Aharonov-Bohm potential

In the framework of QED we evaluate the cross section for electron-positron pair production by a single photon in the presence of the external Aharonov-Bohm potential in first order of perturbation theory. We analyse energy, angular and polarization distributions at different energy regimes: near the threshold and at high photon energies.Comment: LaTeX file, 13 page

The formation of Uranus and Neptune among Jupiter and Saturn

The outer giant planets, Uranus and Neptune, pose a challenge to theories of planet formation. They exist in a region of the Solar System where long dynamical timescales and a low primordial density of material would have conspired to make the formation of such large bodies ($\sim$ 15 and 17 times as massive as the Earth, respectively) very difficult. Previously, we proposed a model which addresses this problem: Instead of forming in the trans-Saturnian region, Uranus and Neptune underwent most of their growth among proto-Jupiter and -Saturn, were scattered outward when Jupiter acquired its massive gas envelope, and subsequently evolved toward their present orbits. We present the results of additional numerical simulations, which further demonstrate that the model readily produces analogues to our Solar System for a wide range of initial conditions. We also find that this mechanism may partly account for the high orbital inclinations observed in the Kuiper belt.Comment: Submitted to AJ; 38 pages, 16 figure

Vortex phases in mesoscopic cylinders with suppressed surface superconductivity

Vortex structures in mesoscopic cylinder placed in external magnetic field are studied under the general de Gennes boundary condition for the order parameter corresponding to the suppression of surface superconductivity. The Ginzburg-Landau equations are solved based on trial functions for the order parameter for vortex-free, single-vortex, multivortex, and giant vortex phases. The equilibrium vortex diagrams in the plane of external field and cylinder radius and magnetization curves are calculated at different values of de Gennes "extrapolation length" characterizing the boundary condition for the order parameter. The comparison of the obtained variational results with some available exact solutions shows good accuracy of our approach.Comment: RevTex, 11 pages, 10 figure

Quasi-two-dimensional electron system at the interface between antiferromagnet LaMnO3 and ferroelectric Ba0.8Sr0.2TiO3

The reported study was funded by Russian Scientific Foundation according to the research project No. 18-12-00260