Quasiparticle Effective Mass for the Two- and Three-Dimensional Electron Gas

We calculate the quasiparticle effective mass for the electron gas in two and three dimensions in the metallic region. We employ the single particle scattering potential coming from the Sj\"{o}lander-Stott theory and enforce the Friedel sum rule by adjusting the effective electron mass in a scattering calculation. In 3D our effective mass is a monotonically decreasing function of $r_s$ throughout the whole metallic domain, as implied by the most recent numerical results. In 2D we obtain reasonable agreement with the experimental data, as well as with other calculations based on the Fermi liquid theory. We also present results of a variety of different treatments for the effective mass in 2D and 3D.Comment: 12 pages, 2 figure

Nonlinear screening in two-dimensional electron gases

We have performed self-consistent calculations of the nonlinear screening of a point charge Z in a two-dimensional electron gas using a density functional theory method. We find that the screened potential for a Z=1 charge supports a bound state even in the high density limit where one might expect perturbation theory to apply. To explain this behaviour, we prove a theorem to show that the results of linear response theory are in fact correct even though bound states exist.Comment: 4 pages, 4 figure

Electronic Band Structure In A Periodic Magnetic Field

We analyze the energy band structure of a two-dimensional electron gas in a periodic magnetic field of a longitudinal antiferromagnet by considering a simple exactly solvable model. Two types of states appear: with a finite and infinitesimal longitudinal mobility. Both types of states are present at a generic Fermi surface. The system exhibits a transition to an insulating regime with respect to the longitudinal current, if the electron density is sufficiently low.Comment: 8 pages, 5 figures; to appear in Phys. Rev. B '9

INTERLAYER VORTICES AND EDGE DISLOCATIONS IN HIGH TEMPERATURE SUPERCONDUCTORS

The interaction of an edge dislocation made of half the superconducting plane with a magnetic interlayer vortex is considered within the framework of the Lawrence-Doniach model with negative as well as positive Josephson interlayer coupling. In the first case the binding energy of the vortex and the dislocation has been calculated by employing a variational procedure. The current distribution around the bound vortex turns out to be asymmetric. In the second case the dislocation carries a spontaneous magnetic half-vortex, whose binding energy with the dislocation turns out to be infinite. The half-vortex energy has been calculated by the same variational procedure. Implications of the possible presence of such half-vortices for the properties of high temperature superconductors are discussed.Comment: 14 Latex pages, 1 figure available upon request

Resonant peak splitting for ballistic conductance in magnetic superlattices

We investigate theoretically the resonant splitting of ballistic conductance peaks in magnetic superlattices. It is found that, for magnetic superlattices with periodically arranged $n$ identical magnetic-barriers, there exists a general $(n-1)$-fold resonant peak splitting rule for ballistic conductance, which is the analogy of the $(n-1)$-fold resonant splitting for transmission in $n$-barrier electric superlattices (R. Tsu and L. Esaki, Appl. Phys. Lett. {\bf 22}, 562 (1973)).Comment: 9 pages, 3 figures, latex forma

ФОРМАЛИЗАЦИЯ СЕЛЕКТИВНОЙ ТЕХНОЛОГИИ СОДЕРЖАНИЯ ИНФРАСТРУКТУРЫ И СТРАХОВОЙ ФОНД

Any failure of technical means or abnormal operation situation reduces the intensity of rail traffic, significantly affects economic and operational performance of the transport market actors. In recent years, these complex processes have additionally been affected by threats caused by adverse changes in the economy and irregularities in the organization of transportation [1, 2]. So it is necessary to move from a traditional (situational) technology to a new one, «preventive», which is determined by means of monitoring and diagnostics based on a missed freight turnover and structural features of the track superstructure. The objective of the authors is to investigate a selective technology of repair and maintenance of the track superstructure.The proposed technology is called selective because it is focused on repair of infrastructure on the fact (optionally, selectively). Selection implies the existence of an insurance or safety fund, which performs two functions: it collects payments with varying frequency to perform various types of repair work, and then as needed pays for these works. Cash flows related to the insurance fund, are structured and designed for a specific frequency of use, and the state of the fund itself is described by a random process of risk. Assessment of technological risk indicators and measures of reliability is given by simulation.Предложено математическое обеспечение для формализации селективной технологии ремонта верхнего строения пути, основанной на обслуживании по «фактическому состоянию». Селективная (выборочная) технология предполагает наличие страхового фонда, который выполняет две функции: накапливает платежи с различной периодичностью для выполнения различного вида ремонтных работ, а затем по мере необходимости оплачивает эти работы. Денежные потоки, связанные со страховым фондом, структурированы и рассчитаны на определенную периодичность использования, а само состояние фонда описывается случайным процессом риска. Оценка показателей технологического риска и меры достоверности дается с помощью имитационного моделирования

The Cyberattack Intensity Forecasting to Information Systems of Critical Infrastructures

В нормативных документах последних лет в сфере информационной безопасности уделяется большое внимание информационным системам критических инфраструктур. Это, в свою очередь, обосновывает необходимость научных исследований по разработке новых методов защиты от кибератак на такие информационные системы. Для этой задачи рекомендуется интервальное прогнозирование на основе вероятностной нейронной сети с динамическим обновлением параметра сглаживания. В качестве эталонов для сравнения результатов интервального прогнозирования были выбраны наивная байесовская модель и вероятностная кластерная модель.In regulatory documents of recent years in the field of information security, much attention is paid to information systems of critical infrastructures. This, in turn, justifies the need for scientific research on the development of new methods of protection against cyberattacks on such information systems. For this task, interval forecasting is recommended based on a probabilistic neural network with dynamic updating of the smoothing parameter. As benchmarks for comparing the interval forecasting results, the naive Bayesian model and the probabilistic cluster model were chosen

Self-similarity and novel sample-length-dependence of conductance in quasiperiodic lateral magnetic superlattices

We study the transport of electrons in a Fibonacci magnetic superlattice produced on a two-dimensional electron gas modulated by parallel magnetic field stripes arranged in a Fibonacci sequence. Both the transmission coefficient and conductance exhibit self-similarity and the six-circle property. The presence of extended states yields a finite conductivity at infinite length, that may be detected as an abrupt change in the conductance as the Fermi energy is varied, much as a metal-insulator transition. This is a unique feature of transport in this new kind of structure, arising from its inherent two-dimensional nature.Comment: 9 pages, 5 figures, revtex, important revisions made. to be published in Phys. Rev.

Quadratic electronic response of a two-dimensional electron gas

The electronic response of a two-dimensional (2D) electron system represents a key quantity in discussing one-electron properties of electrons in semiconductor heterojunctions, on the surface of liquid helium and in copper-oxide planes of high-temperature superconductors. We here report an evaluation of the wave-vector and frequency dependent dynamical quadratic density-response function of a 2D electron gas (2DEG), within a self-consistent field approximation. We use this result to find the $Z_1^3$ correction to the stopping power of a 2DEG for charged particles moving at a fixed distance from the plane of the 2D sheet, $Z_1$ being the projectile charge. We reproduce, in the high-density limit, previous full nonlinear calculations of the stopping power of a 2DEG for slow antiprotons, and we go further to calculate the $Z_1^3$ correction to the stopping power of a 2DEG for a wide range of projectile velocities. Our results indicate that linear response calculations are, for all projectile velocities, less reliable in two dimensions than in three dimensions.Comment: 17 pages, 5 figures, to appear in Phys. Rev.