253 research outputs found
A model of a pumped continuous atom laser
We present a model of a cw atom laser based on a system of coupled GP
equations. The model incorporates continuous Raman outcoupling, pumping and
three-body recombination. The outcoupled field has minimal atomic density
fluctuations and is locally monochromatic.Comment: 10 pages, 8 eps figures, typos fixe
Angular Momenta and Spin-Orbit Interaction of Nonparaxial Light in Free Space
We give an exact self-consistent operator description of the spin and orbital
angular momenta, position, and spin-orbit interactions of nonparaxial light in
free space. Both quantum-operator formalism and classical energy-flow approach
are presented. We apply the general theory to symmetric and asymmetric Bessel
beams exhibiting spin- and orbital-dependent intensity profiles. The exact wave
solutions are clearly interpreted in terms of the Berry phases, quantization of
caustics, and Hall effects of light, which can be readily observed
experimentally.Comment: 8 pages, 3 figure
Incoherent excitation and switching of spin states in exciton-polariton condensates
We investigate, theoretically and numerically, the spin dynamics of a
two-component exciton-polariton condensate created and sustained by
non-resonant spin-polarized optical pumping of a semiconductor microcavity.
Using the open-dissipative mean-field model, we show that the existence of well
defined phase-locked steady states of the condensate may lead to efficient
switching and control of spin (polarization) states with a non-resonant
excitation. Spatially inhomogeneous pulsed excitations can cause symmetry
breaking in the pseudo-spin structure of the condensate and lead to formation
of non-trivial spin textures. Our model is universally applicable to two weakly
coupled polariton condensates, and therefore can also describe the behaviour of
condensate populations and phases in 'double-well' type potentials
Bistability in Microcavities with Incoherent Optical or Electrical Excitation
We consider a quantum well embedded in a zero-dimensional microcavity with a
sub-wavelength grated mirror, where the x-linearly polarized exciton mode is
strongly coupled to the cavity photon, while y-polarized excitons remain in the
weak coupling regime. Under incoherent optical or electric pumping, we
demonstrate polariton bistability associated with parametric scattering
processes. Such bistability is useful for constructing polaritonic devices with
optical or electrical incoherent pumping.Comment: 5 pages, 3 figure
Instability-induced formation and non-equilibrium dynamics of phase defects in polariton condensates
We study, theoretically and numerically, the onset and development of
modulational instability in an incoherently pumped spatially homogeneous
polariton condensate. Within the framework of mean-field theory, we identify
regimes of modulational instability in two cases: 1) Strong feedback between
the condensate and reservoir, which may occur in scalar condensates, and 2)
Parametric scattering in the presence of polarization splitting in spinor
condensates. In both cases we investigate the instability induced textures in
space and time including non-equilibrium dynamics of phase dislocations and
vortices. In particular we discuss the mechanism of vortex destabilization and
formation of spiraling waves. We also identify the presence of topological
defects, which take the form of half-vortex pairs in the spinor case, giving an
"eyelet" structure in intensity and dipole type structure in the spin
polarization. In the modulationally stable parameter domains, we observe
formation of the phase defects in the process of condensate formation from an
initially spatially incoherent low-density state. In analogy to the
Kibble-Zurek type scaling for nonequilibrium phase transitions, we find that
the defect density scales with the pumping rate.Comment: 13 pages, 9 figures, revised manuscript sent to Phys. Rev.
Tradition as a Homeland to Return to: Transnational Religious Identity of the Post-Soviet Orthodox Jewry
Received 26 April 2021. Accepted 14 May 2021. Published online 9 July 2021.This article highlights the outcome of a long-term field research into the transnational identity of the post-Soviet Orthodox Jewry. It analyzes biographical interviews taken between 2015 and 2018 in St. Petersburg and Minsk to define the religious identity and day-to-day practices of post-Soviet Orthodox Jews. In this article, I argue that the communities of post-Soviet Orthodox Jews is a new socio-cultural phenomenon with no historical prototypes. As to the research methodology, it was a combination of the transnational approach, random choice casestudy targeting post-Soviet Orthodox communities of Orthodox Jewry in large cities, and the biographical method. The backbone of the post-Soviet Orthodox communities of different strains of Judaism was formed in 1990–2008. It is made up of three generations of men and women born in the late 1940s–1960s, mid-1960s–early 1970s, and the 1980s. Each of these generations is characterized by its own unique pattern of observance, the formation of which is directly conditioned by the circumstances of involvement in religious Jewry. The transnational pattern of observance of the Post-Soviet Orthodox Jews involves the model they confronted at the very beginning of their journey, the model they learned in overseas educational institutions or through incoming envoys and rabbis in the country of residence, and the model of balance between the required and possible in the modern post-Christian and post-atheist environment
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