Breit-Wheeler Process in Intense Short Laser Pulses

Energy-angular distributions of electron-positron pair creation in collisions of a laser beam and a nonlaser photon are calculated using the $S$-matrix formalism. The laser field is modeled as a finite pulse, similar to the formulation introduced in our recent paper in the context of Compton scattering [Phys. Rev. A {\bf 85}, 062102 (2012)]. The nonperturbative regime of pair creation is considered here. The energy spectra of created particles are compared with the corresponding spectra obtained using the modulated plane wave approximation for the driving laser field. A very good agreement in these two cases is observed, provided that the laser pulse is sufficiently long. For short pulse durations, this agreement breaks down. The sensitivity of pair production to the polarization of a driving pulse is also investigated. We show that in the nonperturbative regime, the pair creation yields depend on the polarization of the pulse, reaching their maximal values for the linear polarization. Therefore, we focus on this case. Specifically, we analyze the dependence of pair creation on the relative configuration of linear polarizations of the laser pulse and the nonlaser photon. Lastly, we investigate the carrier-envelope phase effect on angular distributions of created particles, suggesting the possibility of phase control in relation to the pair creation processes.Comment: 13 pages, 8 figure

Muon pair creation from positronium in a circularly polarized laser field

We study elementary particle reactions that result from the interaction of an atomic system with a very intense laser wave of circular polarization. As a specific example, we calculate the rate for the laser-driven reaction $e^+e^- \to \mu^+\mu^-$, where the electron and positron originate from a positronium atom or, alternatively, from a nonrelativistic $e^+e^-$ plasma. We distinguish accordingly between the coherent and incoherent channels of the process. Apart from numerical calculations, we derive by analytical means compact formulas for the corresponding reaction rates. The rate for the coherent channel in a laser field of circular polarization is shown to be damped because of the destructive interference of the partial waves that constitute the positronium ground-state wave packet. Conditions for the observation of the process via the dominant incoherent channel in a circularly polarized field are pointed out

Энергетическая проблема. Атом как неиссякаемый источник экологически чистой энергии

The fundamentally new approach to the power problem is put forward based on the excitation of electronic quantum transitions in atom responsible for the increase in mass defect of atom. The consecutive quantum theory of hydrogen atom as a system of two particles interacting with each other — electron and proton is constructed on the basis of Dirac’s model of electron. The motion of nucleus in the hydrogen atom is shown to essentially affect the physical properties of atom. The en-ergy spectrum of the atom contains two regions of bound states of electron and nucleus separated from each other by energy of the order of 2m2c2 (m2 is the mass of proton, c is the velocity of light). As a consequence, there exist such states of the atom in which the mass defect of atom reaches the value of 2m1 (m1 is the mass of electron). The existence of quantum states of atom with abnormally high mass defect and the ability of atom to make transitions from states with smaller value of mass defect to states with greater value open the prospect of creation of active thermal machines (TM) producing superfluous energy, i.e. transforming the energy of environment to active form. From the conceptual point of view, the idea of production of superfluous energy in active TM does not differ from the physical idea which is carried out in the thoroughly studied reactions of thermonuclear synthesis. In both cases, the question is the organization and maintenance in a system of interacting particles of physical processes in which the state of system changes in such a manner that the mass defect of sys-tem eventually increases in comparison with mass defect in initial state. Distinction between active TM and thermonuclear reactor consists only in the fact that physical processes of various types are used in them: in the first case — electronic processes in atoms, and in the second one — the processes going on at collision of nucleons and nuclei. The fact that both phenomena — the produc-tion of superfluous energy in active TM and the energy liberation in reaction of thermonuclear synthe-sis — are of the same physical nature and are described by the same parameter — mass defect means that production of superfluous energy is as real as thermonuclear synthesis. As the energy liberation in active TM occurs due to electronic processes in atoms instead of synthesis or splitting of atomic nu-clei, active TM will be ecologically pure energy sources. As fuel for active thermal machine, any substance can serve, the atoms of which can be in states with various values of mass defect. The re-sults of the present work do not contradict the laws of thermodynamics. The principles of action of TM described in textbooks on thermodynamics refer only to such TM which are isolated from envi-ronment (such TM can be naturally referred to as passive). The idea that it is impossible to trans-form energy of environment to active form, deeply rooted in consciousness, is the deepest and tragic delusion of the last century resulted in the orientation of economy of the planet exclusively towards passive TM. Consequences are known: research on the transformation of environment energy to active form (N.Tesla, K.E.Tsiolkovsky, P.K.Oshchepkov, etc.) have been blocked and declared as pseudo science, and the mankind appeared on the verge of ecological catastrophe by the end of the century. The real way toward resolving power problem, as is evident from the results of the paper, passes through the research directed towards the creation of active thermal machines — qualitatively new ecologically pure energy sources.Предложен принципиально новый подход к энергетической проблеме, в основе которого лежит возбуждение в электронной подсистеме атома квантовых переходов, приводящих к увеличению дефекта массы атома. Исходя из дираковской модели электрона, построена последовательная квантовая теория атома водорода как системы двух взаимодействующих между собой частиц — электрона и протона. Показано, что движение ядра в атоме водорода существенно влияет на физические свойства атома. Энергетический спектр атома содержит две области связанных состояний электрона и ядра, разделенные между собой энергией порядка 2m2c2 (m2 — масса протона, c — скорость света). Вследствие этого, имеются такие состояния атома, в которых дефект массы атома достигает значения 2m1 (m1 — масса электрона). Существование квантовых состояний атома с аномально высоким дефектом массы и способность атома совершать переходы из состояний с меньшим значением дефекта массы в состояния с большим значением открывают перспективу создания активных тепловых машин (ТМ), производящих избыточную энергию, т.е. преобразующих энергию окружающей среды в активную форму. С принципиальной точки зрения идея получения избыточной энергии в активной ТМ не отличается от физической идеи, осуществляемой в хорошо изученных реакциях термоядерного синтеза. В обоих случаях речь идет об организации и поддержании в системе взаимодействующих частиц физических процессов, в которых состояние системы изменяется таким образом, что дефект массы системы с течением времени увеличивается по сравнению с дефектом массы в начальном состоянии. Различие между активной ТМ и термоядерным реактором заключается лишь в том, что в них используются физические процессы различных типов: в первом случае — электронные процессы в атомах, а во втором — процессы, протекающие при столкновении нуклонов и ядер. То обстоятельство, что оба явления — получение избыточной энергии в активной ТМ и освобождение энергии в реакции термоядерного синтеза — имеют одну и ту же физическую природу и описываются одной и той же величиной — дефектом массы, означает, что возможность получения избыточной энергии столь же реальна, как и термоядерный синтез. Поскольку в активных ТМ энерговыделение происходит за счет электронных процессов в атомах, а не в результате синтеза или расщепления атомных ядер, то активные ТМ будут экологически безопасными источниками энергии. Топливом для активной тепловой машины может служить любое вещество, атомы которого могут находиться в состояниях с различными значениями дефекта массы. Результаты настоящей работы не противоречат законам термодинамики. Схема и принципы действия ТМ, описываемые в учебниках по термодинамике, относятся лишь к таким ТМ, которые изолированы от окружающей среды (такие ТМ естественно назвать пассивными). Представление о принципиальной невозможности превращения энергии окружающей среды в активную форму, глубоко укоренившееся в сознании, является глубочайшим и трагическим заблуждением прошлого века, приведшим к ориентации экономики планеты исключительно на пассивные ТМ. Последствия известны: исследования по преобразованию энергии среды в активную форму (Н. Тесла, К.Э. Циолковский, П.К.Ощепков и др.) были заблокированы и объявлены лженаукой, и человечество к концу века оказалось на грани экологической катастрофы. Реальный путь к решению энергетической проблемы, как видно из результатов работы, лежит через исследования, направленные на создание активных ТМ — качественно новых экологически чистых источников энергии

Essential self-adjointness of magnetic Schr\"odinger operators on locally finite graphs

We give sufficient conditions for essential self-adjointness of magnetic Schr\"odinger operators on locally finite graphs. Two of the main theorems of the present paper generalize recent results of Torki-Hamza.Comment: 14 pages; The present version differs from the original version as follows: the ordering of presentation has been modified in several places, more details have been provided in several places, some notations have been changed, two examples have been added, and several new references have been inserted. The final version of this preprint will appear in Integral Equations and Operator Theor

Time, what is it? Dynamical Properties of Time 1

Abstract. The phenomenon of local dynamical inhomogeneity of time is predicted, which implies that the course of time along the trajectory of motion of a particle in the inertial reference frames moving relative to each other depends on the state of motion of the particle under the influence of a force field. As is seen from the results obtained, the ability to influence the course of time represents one of the most fundamental properties of any material system intrinsically inherent in it by the very nature of things, which manifests itself when the system interacts with force fields. The inferences of the paper are not based on the use of any hypotheses and strictly follow from relativistic equations of motion. The dependence of the course of time upon the behaviour of physical system is, thus, a direct consequence of causality principle, relativity principle and the pseudoeuclidity of space-time. The results obtained confirm the Kozyrev hypothesis that time has physical properties and open up radically new opportunities for the efficient control of physical processes. It is demonstrated with point particle that the change in the course of time results in the appearance of an additional force acting on the particle. A general conclusion is drawn on the basis of the theory advanced that relativistic equations of motion for any kind of matter contain information about the physical properties of time, which are, thus, of dynamical nature

Numerical study of oil spill in the Patos lagoon under flood and ebb conditions

Facing great obstacles to eradicate environmental hazards generated by oil spills, it is crucial to establish actions against such accidents. In this context, the focus of this study is to analyze oil spills at the harbor region of Rio Grande, Rio Grande do Sul. The Easy Coupling Oil System (ECOS) model was used to model the oil spills under different environmental conditions simulated by the hydrodynamic model Telemac-3D, with the intention to identify the main forces controlling the movement of the oil slicks over a year of averaged hydrodynamic conditions from 2003 to 2015. The computational domain comprises the Patos Lagoon, the harbor area of Rio Grande and the Southern Brazilian Shelf. For the oil spill simulations, eight distinct events were defined considering both flood and ebb conditions in the estuarine region of the Patos Lagoon. The oil spill simulations showed that, in ebb conditions, the oil slick movement is mainly ruled by the currents, moving towards the outflow. After a few hours, the wind action makes the slick move towards the margins of the waterway. In flood conditions, on the other hand, the oil slick drifts to the interior of the estuary, following the dominant currents and the local winds