Faddeev approach to confined three-quark problems

We propose a method that allows for the efficient solution of the three-body Faddeev equations in the presence of infinitely rising confinement interactions. Such a method is useful in calculations of nonrelativistic and especially semirelativistic constituent quark models. The convergence of the partial wave series is accelerated and possible spurious contributions in the Faddeev components are avoided. We demonstrate how the method works with the example of the Goldstone-boson-exchange chiral quark model for baryons.Comment: 6 page

Deflagration to Detonation Transition in Thermonuclear Supernovae

We derive the criteria for deflagration to detonation transition (DDT) in a Type Ia supernova. The theory is based on the two major assumptions: (i) detonation is triggered via the Zeldovich gradient mechanism inside a region of mixed fuel and products, (ii) the mixed region is produced by a turbulent mixing of fuel and products either inside an active deflagration front or during the global expansion and subsequent contraction of an exploding white dwarf. We determine the critical size of the mixed region required to initiate a detonation in a degenerate carbon-oxygen mixture. This critical length is much larger than the width of the reaction front of a Chapman-Jouguet detonation. However, at densities greater than simeq 5 x 10^6 g cm^-3, it is much smaller than the size of a white dwarf. We derive the critical turbulent intensity required to create the mixed region inside an active deflagration front in which a detonation can form. We conclude that the density rho_tr at which a detonation can form in a carbon-oxygem white dwarf is low, less than 2 - 5 x 10^7 g cm^-3, but greater than 5 x 10^6 g cm^-3.Comment: 28 pages, 19 figs, Latex (epsf), submitted to The Astrophysical Journa

О ЧИСЛЕННОЙ ОЦЕНКЕ ЭФФЕКТИВНЫХ УПРУГИХ ХАРАКТЕРИСТИК ЭЛАСТОМЕРНЫХ КОМПОЗИТОВ ПРИ КОНЕЧНЫХ ДЕФОРМАЦИЯХ С ИСПОЛЬЗОВАНИЕМ МЕТОДА СПЕКТРАЛЬНЫХ ЭЛЕМЕНТОВ С ПОМОЩЬЮ CAE FIDESYS

Estimation of effective properties of composite materials is one of the main problems for the composite mechanics. In this article, a method is developed by which the effective nonlinear elastic  properties of elastomer composites (filled rubbers) are estimated  under finite strains. The method is based on numerical solution of  nonlinear elastic boundaryvalue problems for a representative  volume element (RVE) of elastomer composite. Different boundary  conditions are consequently applied to the RVE: nonperiodic  (displacements of the RVE boundary) or periodic (restraints on  displacements of corresponding points of opposite faces of RVE). An obtained stress field is averaged by volume after the solution of an  elastic boundary-value problem. Effective properties are estimated  as a quadratic dependence of the second Piola-Kirchhoff stress  tensor upon the Green strain tensor. This article presents the results of numerical estimation of effective elastic properties of filled  rubbers under finite strains. Numerical calculations were performed  with the help of Fidesys Composite program module, which is a part  of the domestic Fidesys CAE-system, using the finite element method and the spectral element method. Spectral element method  is one of the most effective and modern finite element method  version. High order piecewice-polynomial functions are reference functions in SEM. There is no need to rebuild or refine mesh to check solution mesh convergence, as mesh is kept in initial state and only  element orders are changed. The subject of investigation was the  filled elastomer effective properties dependence upon the filler  particles special orientation and the filling degree. Graphs of these dependencies are given in the article. The obtained results show that the spectral element method is suitable for numerical solution of the effective properties estimation problem for composite materials. In  addition, the results allow to estimate the influence of non-linear  effects upon the mechanical properties of the composite. The correction for stress from taking the non-linearity into account is  about 25% under the strain 15% in the case of uniaxial tension.Одной из основных задач механики композитов является оценка эффективных  характеристик композиционного материала. В данной работе описывается методика  численной оценки эффективных нелинейно-упругих характеристик применительно к  эластомерным композитам (наполненным резинам), при конечных деформациях. Методика основана на численном решении краевых задач нелинейной теории упругости на  представительном объёме эластомерного композита. К представительному объёму  последовательно прикладываются различные граничные условия: непериодические (в виде  жёстко заданных перемещений каждой точки границы) либо периодические (в виде связей,  наложенных на перемещения точек противоположных граней представительного объёма,  проекции которых на эти грани совпадают). После решения краевой задачи упругости  полученное поле напряжений осредняется по объёму. Эффективные свойства оцениваются в виде квадратичной зависимости второго тензора напряжений Пиолы-Кирхгофа от тензора  деформаций Грина. В статье представлены результаты численной оценки эффективных  упругих характеристик наполненных резин при конечных деформациях. Численные расчёты проводились с помощью программного модуля Fidesys Composite, входящего в состав отечественной CAE-системы Fidesys, с использованием метода конечных элементов и метода спектральных элементов. Метод спектральных элементов является более современной и эффективной версией метода конечных элементов. В нём в качестве базисных функций  используются кусочно-полиномиальные функции высоких порядков. При работе с моделью  у пользователя отсутствует необходимость перестроения и измельчения сетки для проверки  сеточной сходимости полученного решения, поскольку сетка может оставаться изначальной, а изменяться только порядок элементов. Исследовались зависимости эффективных свойств  наполненного эластомера от пространственной ориентации частиц наполнителя и от степени наполнения. Графики этих зависимостей приведены в статье. Полученные результаты  свидетельствуют о применимости метода спектральных элементов к численному решению задачи оценки эффективных свойств композитов. Также полученные результаты позволяют  оценить влияние нелинейных эффектов на механические свойства композита. Так,  например, при одноосном растяжении величиной деформации порядка 15% поправка от  учёта нелинейных эффектов для напряжения в направлении той же оси составит примерно 25%

On the Possibility of the Detection of Extinct Radio Pulsars

We explore the possibilities for detecting pulsars that have ceased to radiate in the radio band. We consider two models: the model with hindered particle escape from the pulsar surface (first suggested by Ruderman and Sutherland 1975) and the model with free particle escape (Arons 1981; Mestel 1999). In the model with hindered particle escape, the number of particles that leave the pulsar magnetosphere is small and their radiation cannot be detected with currently available instruments. At the same time, for the free particle escape model, both the number of particles and the radiation intensity are high enough for such pulsars to be detectable with the presently available receivers such as GLAST and AGILE spacecrafts. It is also possible that extinct radio pulsars can be among the unidentified EGRET sources.Comment: 5 pages, 1 figure corrected version of the paper that was published in Astronomy Letter

Magnetooptical Study of Zeeman Effect in Mn modulation-doped InAs/InGaAs/InAlAs Quantum Well Structures

We report on a magneto-photoluminescence (PL) study of Mn modulation-doped InAs/InGaAs/InAlAs quantum wells. Two PL lines corresponding to the radiative recombination of photoelectrons with free and bound-on-Mn holes have been observed. In the presence of a magnetic field applied in the Faraday geometry both lines split into two circularly polarized components. While temperature and magnetic field dependences of the splitting are well described by the Brillouin function, providing an evidence for exchange interaction with spin polarized manganese ions, the value of the splitting exceeds the expected value of the giant Zeeman splitting by two orders of magnitude for a given Mn density. Possible reasons of this striking observation are discussed

Hard X-ray Bursts from Collapse of the Super Massive Stars

The very first stars in the Universe can be very massive, up to $10^6M_\odot$. They would leave behind massive black holes that could act as seeds for growing super massive black holes of active galactic nuclei. Given the anticipated fast rotation such stars would end their live as super massive collapsars and drive powerful magnetically-dominated jets. In this paper we investigate the possibility of observing the bursts of high-energy emission similar to the Long Gamma Ray Bursts associated with normal collapsars. We show that during the collapse of supercollapsars, the Blandford-Znajek mechanism can produce jets as powerful as few$\times10^{51}$erg/s and release up to $10^{56}$erg of the black hole rotational energy. Due to the higher intrinsic time scale and higher redshift the initial bright phase of the burst can last for about $10^5$ seconds whereas the central engine would remain active for about 10 days. Due to the high redshift the burst spectrum is expected to be soft, with the spectral energy distribution peaking at around 60keV. The peak total flux density is relatively low, few$\times 10^{-7}erg\, cm^{-2} s^{-1}$, but not prohibitive. The such events should be rear 0.03 year$^{-1}$, the observations needs long term program and could be done in future.Comment: 4 pages, 2 figures. proceedings of workshop "Many faces of GRB phenomena - optics vs high energy", SAO Russia, October 12-16, 2009