649 research outputs found
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 -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
National natural park “Svyatie gory” is a perspective destination for the development of recreation and ecotourism
Interior error estimate for periodic homogenization
In a previous article about the homogenization of the classical problem of
diff usion in a bounded domain with su ciently smooth boundary we proved that
the error is of order . Now, for an open set with su ciently
smooth boundary and homogeneous Dirichlet or Neuman limits conditions
we show that in any open set strongly included in the error is of order
. If the open set is of polygonal (n=2) or
polyhedral (n=3) boundary we also give the global and interrior error
estimates
IMPLEMENTATION AND TESTING OF A POWER MATRIX-BASED WAVE ENERGY CONVERSION MODEL AND THE EFFECT SIMULATED ON THE WAVE FIELD — CASE STUDY OF LAGUNA, SC, BRAZIL
Electrical energy has become an essential resource for mankind and, as the population and technological dependency grow, also does the electricity demand. This necessity boosted numerous studies which focus on clean and renewable energy sources. Ocean wave energy is one of the most environmentally friendly sources of energy since it does not emit pollutants to the atmosphere and does not produce harmful waste. Another positive point about ocean waves is that they are inexhaustible, therefore a power plant could, potentially, provide energy indefinitely. Hence the object of this study is to estimate the wave energy reduction caused by the presence of wave energy conversion (WEC) devices near the coastline of Laguna, Brazil. In order to study the coastal impact of a WEC farm, the third generation sea state model TOMAWAC was used to simulate the waves on the Southern Brazilian Shelf under two different conditions, with and without the presence of an array of WECs. The results show that the mean significant wave height in the blockaded area undergoes a slight drop, caused by the presence of the WECs, which do not appear in the other scenario. But this reduction of the significant wave height is negligible compared to the order of magnitude of the wave height itself
Particle dynamics inside shocks in Hamilton-Jacobi equations
Characteristics of a Hamilton-Jacobi equation can be seen as action
minimizing trajectories of fluid particles. For nonsmooth "viscosity"
solutions, which give rise to discontinuous velocity fields, this description
is usually pursued only up to the moment when trajectories hit a shock and
cease to minimize the Lagrangian action. In this paper we show that for any
convex Hamiltonian there exists a uniquely defined canonical global nonsmooth
coalescing flow that extends particle trajectories and determines dynamics
inside the shocks. We also provide a variational description of the
corresponding effective velocity field inside shocks, and discuss relation to
the "dissipative anomaly" in the limit of vanishing viscosity.Comment: 15 pages, no figures; to appear in Philos. Trans. R. Soc. series
ANALYSIS OF SHIP BEHAVIOR UNDER INFLUENCE OF WAVES AND CURRENTS
The most important environmental factors related to safety of ship and performance on high sea are surface winds and waves. In order to obtain an optimal trajectory of a ship route, it is a prerequisite to know the sea state condition, as well as, the behavior of the ship in waves and currents. The purpose of this study is to analyze the ship behavior under the influence of 3 different sea state conditions over the Southern Brazilian inner shelf near the Rio Grande coastal region. SHIPMOVE and TOMAWAC + TELEMAC3D system were simulated under three different wave scenarios. Day 4 showed the shortest traveled distance and lowest velocity. The sea state of Day 33 deflected the initial vessel path northeasterly and generated high rotational motions. Day 100 depicted the longest final displacement and highest average velocity, where this event showed the most smooth sea state condition. Lastly, the ship behavior seems to be strongly influenced by the sea state condition for the three events
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