Photon recoil momentum in a Bose-Einstein condensate of a dilute gas

We develop a "minimal" microscopic model to describe a two-pulse-Ramsay-interferometer-based scheme of measurement of the photon recoil momentum in a Bose-Einstein condensate of a dilute gas [Campbell et al., Phys. Rev. Lett. 94, 170403 (2005)]. We exploit the truncated coupled Maxwell-Schroedinger equations to elaborate the problem. Our approach provides a theoretical tool to reproduce essential features of the experimental results. Additionally, we enable to calculate the quantum-mechanical mean value of the recoil momentum and its statistical distribution that provides a detailed information about the recoil event.Comment: 6 pages, 4 figure

Diagrammatic quantum field formalism for localized electrons

We introduce a diagrammatic quantum field formalism for the evaluation of normalized expectation values of operators, and suitable for systems with localized electrons. It is used to develop a convergent series expansion for the energy in powers of overlap integrals of single-particle orbitals. This method gives intuitive and practical rules for writing down the expansion to arbitrary order of overlap, and can be applied to any spin configuration and to any dimension. Its applicability for systems with well localized electrons has been illustrated with examples, including the two-dimensional Wigner crystal and spin-singlets in the low-density electron gas.Comment: 13 pages, 0 figure

Photon Recoil in Light Scattering by a Bose-Einstein Condensate of a Dilute Gas

Abstract: Photon recoil upon light scattering by a Bose–Einstein condensate (BEC) of a dilute atomic gas is analyzed theoretically accounting for a weak interatomic interaction. Our approach is based on the Gross–Pitaevskii equation for the condensate, which is coupled to the Maxwell equation for the field. The dispersion relations of recoil energy and momentum are calculated, and the effect of weak nonideality of the condensate on the photon recoil is ubraveled. A good agreement between the theory and experiment [7] on the measurement of the photon recoil momentum in a dispersive medium is demonstrated

Rayleigh superradiance and dynamic Bragg gratings in an end-pumped Bose-Einstein condensate

We study experimentally superradiant Rayleigh scattering from a Bose-Einstein condensate (BEC) in a new parameter regime where pump depletion and the exchange of photons between the endfire modes are important. Through experiments and simulations we show that collective atom light coupling leads to the self-organized formation of dynamic Bragg gratings within the sample. These gratings lead to an efficient back-scattering of pump photons and optical resonator structures within the BEC.Comment: 5 pages, 3 figure

Sequential superradiant scattering from atomic Bose-Einstein condensates

We theoretically discuss several aspects of sequential superradiant scattering from atomic Bose-Einstein condensates. Our treatment is based on the semiclassical description of the process in terms of the Maxwell-Schroedinger equations for the coupled matter-wave and optical fields. First, we investigate sequential scattering in the weak-pulse regime and work out the essential mechanisms responsible for bringing about the characteristic fan-shaped side-mode distribution patterns. Second, we discuss the transition between the Kapitza-Dirac and Bragg regimes of sequential scattering in the strong-pulse regime. Finally, we consider the situation where superradiance is initiated by coherently populating an atomic side mode through Bragg diffraction, as in studies of matter-wave amplification, and describe the effect on the sequential scattering process.Comment: 9 pages, 4 figures. Submitted to Proceedings of LPHYS'06 worksho

ОЦЕНКА ЦЕЛОСТНОСТИ ИНФОРМАЦИОННОГО ОБМЕНА В СЕТЯХ СВЯЗИ ТИПОВЫХ АЭРОПОРТОВ

The article considers the evaluation method of information accuracy in communication networks such as radial and ring structure with a single center. The possibility of the assessment probability of communication networks no-failure operation among airport structural divisions with a parallel accounting network fragment resistance to destructive impacts with a probabilistic metrics is given.For probabilities qualimetry of communication network failures use of operative availability function along with recommendations to use theoretical distributions for physically various communication networks is suggested. For a logical chain of the analysis of survival capabilities a range of problems to be stated while making prior and posteriori estimatesis specified.В статье рассмотрена задача методологии оценки достоверности информации в сетях связи типовых аэропортов I…III классов. В качестве базовой структуры для создания модели используется радиально-кольцевой тип с одним центром. Приведены расчетные соотношения для нахождения оценки вероятности безоткатной работы линий связи. Представленные соотношения учитывают сопротивляемость фрагментов сети деструктивным воздействиям, которые описываются вероятностной метрикой. Отдельным является вопрос квалиметрии вероятностей отказов линий связи. Для его решения было предложено использование коэффициента оперативной готовности. Данный коэффициент учитывает физические особенности различных линий связи. Осуществляется поправка коэффициента на характеристики этих линий в соответствии с рекомендациями по использованию теоретических распределений. Обозначен круг конкретных проблем, важных для решения поставленной задачи. Во внимание принимаются актуальные для рассматриваемых сетей уязвимости с учетом их логической взаимосвязи. На основе проведенного анализа цепочки закономерностей между уязвимостями определена методика построения априорных и апостериорных оценок. Представлен пример использования полученных расчетных соотношений

Investigation of pulse shape neutron-gamma discrimination

The role of neutron beam investigation is significant not only for fundamental science but also for various fields of applied science. This work is dedicated to the formation of neutron beams using the external 18-MeV proton beam of IBA cyclotron C18/18 with a beam current of up to 100 µA. The facility is located at the A. Alikhanyan National Science Laboratory (Yerevan Physics Institute). The possibility to obtain thermal or epithermal neutron beams using the external proton beam of the cyclotron is studied using Geant4 simulations. In this case, a quasimonoenergetic neutron source 9Be (p, n)9B reaction is chosen. As a result of the simulations, the optimal thickness of the 9Be beryllium isotope target is determined. The induced neutron beam is accompanied by a gamma ray background. To decrease the number of accompanying gamma rays, the lead absorber is considered. As a method of separating neutrons from gamma rays, the pulse shape discrimination (PSD) technique is developed. This study shows the possibility of neutron-gamma PSD and its applicability using the EJ-299-33A plastic scintillator