Theory of condensation of indirect excitons in a trap

We present theoretical studies of condensation of indirect excitons in a trap. Our model quantifies the effect of screening of the trap potential by indirect excitons on exciton condensation. The theoretical studies are applied to a system of indirect excitons in a GaAs/AlGaAs coupled quantum well structure in a diamond-shaped electrostatic trap where exciton condensation was studied in earlier experiments. The estimated condensation temperature of the indirect excitons in the trap reaches hundreds of milliKelvin

Vortex soliton tori with multiple nested phase singularities in dissipative media

We show the existence of stable two- and three-dimensional vortex solitons carrying multiple, spatially separated, single-charge topological dislocations nested around a vortex-ring core. Such new nonlinear states are supported by elliptical gain landscapes in focusing nonlinear media with two-photon absorption. The separation between the phase dislocations is dictated mostly by the geometry of gain landscape and it only slightly changes upon variation of the gain or absorption strength.Comment: 17 pages, 5 figures, to appear in Physical Review

Compact jets as probes for sub-parsec scale regions in AGN

Compact relativistic jets in active galactic nuclei offer an effective tool for investigating the physics of nuclear regions in galaxies. The emission properties, dynamics, and evolution of jets in AGN are closely connected to the characteristics of the central supermassive black hole, accretion disk and broad-line region in active galaxies. Recent results from studies of the nuclear regions in several active galaxies with prominent outflows are reviewed in this contribution.Comment: AASLaTeX, 5 pages, 4 figures. Accepted in Astrophysics and Space Scienc

On the possibility of refining by means of optical location some astronomical parameters of the system - Earth-Moon

Optical location of moon in Earth-Moon system using artificial light reflector, on lunar surfac

Extragalactic Relativistic Jets and Nuclear Regions in Galaxies

Past years have brought an increasingly wider recognition of the ubiquity of relativistic outflows (jets) in galactic nuclei, which has turned jets into an effective tool for investigating the physics of nuclear regions in galaxies. A brief summary is given here of recent results from studies of jets and nuclear regions in several active galaxies with prominent outflows.Comment: 5 pages; contribution to ESO Astrophysical Symposia, "Relativistic Astrophysics and Cosmology", eds. B. Aschenbach, V. Burwitz, G. Hasinger, B. Leibundgut (Springer: Heidelberg 2006

Neutrino spin rotation in dense matter and electromagnetic field

Exact solutions of the Dirac--Pauli equation for massive neutrino with anomalous magnetic moment interacting with dense matter and strong electromagnetic field are found. The complete system of neutrino wavefunctions, which show spin rotation properties are obtained and their possible applications are discussed.Comment: 11 pages, latex, misprints are correcte

The Effect of Copper and Manganese on the Amorphization Process in a Thin Fe–Si–Mg–O Film

The effect of copper and manganese on the amorphization process in the surface layer of a technical Fe-3% Si alloy during annealing in the α → γ transition temperature range was determined by x-ray phase analysis. The presence of 0.5 wt. % Cu and 0.3 wt. % Mn in the initial Fe-3% Si solid solution significantly enhances the amorphization process that occurs when heated in the temperature range 920… 960∘C as an alternative to the α → γ phase transformation. The effect of amplification of amorphization is both in obtaining a larger amount of material in the amorphous state, and in the appearance of two amorphous phases, differing in average interatomic distance. The composition of the amorphous phase is approximately described as Fe89Si6Mg4Mn0.5Cu0.5 in the presence of Cu and Mn atoms and Fe90Si6Mg4 in the case of their absence in the amorphous layer.     Keywords: amorphization, non-ambient x-ray diffraction, Fe-3%Si, phase transition, thermal stability

The Location of the Core in M81

We report on VLBI observations of M81*, the northwest-southeast oriented nuclear core-jet source of the spiral galaxy M81, at five different frequencies between 1.7 and 14.8 GHz. By phase referencing to supernova 1993J we can accurately locate the emission region of M81* in the galaxy's reference frame. Although the emission region's size decreases with increasing frequency while the brightness peak moves to the southwest, the emission region seems sharply bounded to the southwest at all frequencies. We argue that the core must be located between the brightness peak at our highest frequency (14.8 GHz) and the sharp bound to the southwest. This narrowly constrains the location of the core, or the purported black hole in the center of the galaxy, to be within a region of +/-0.2 mas or +/-800 AU (at a distance of ~4 Mpc). This range includes the core position that we determined earlier by finding the most stationary point in the brightness distribution of M81* at only a single frequency. This independent constraint therefore strongly confirms our earlier core position. Our observations also confirm that M81* is a core-jet source, with a one-sided jet that extends to the northeast from the core, on average curved somewhat to the east, with a radio spectrum that is flat or inverted near the core and steep at the distant end. The brightness peak is unambiguously identified with the variable jet rather than the core, which indicates limitations in determining the proper motion of nearby galaxies and in refining the extragalactic reference frame.Comment: LaTeX, 10 pages with 3 figures. Typos fixed and slight rewording for clarity from previous version. Accepted for publication in the Astrophysical Journa

Controlling circular polarization of light emitted by quantum dots using chiral photonic crystal slab

We study the polarization properties of light emitted by quantum dots that are embedded in chiral photonic crystal structures made of achiral planar GaAs waveguides. A modification of the electromagnetic mode structure due to the chiral grating fabricated by partial etching of the wave\-guide layer has been shown to result in a high circular polarization degree $\rho_c$ of the quantum dot emission in the absence of external magnetic field. The physical nature of the phenomenon can be understood in terms of the reciprocity principle taking into account the structural symmetry. At the resonance wavelength, the magnitude of $|\rho_c|$ is predicted to exceed 98%. The experimentally achieved value of $|\rho_c|=81$% is smaller, which is due to the contribution of unpolarized light scattered by grating defects, thus breaking its periodicity. The achieved polarization degree estimated removing the unpolarized nonresonant background from the emission spectra can be estimated to be as high as 96%, close to the theoretical prediction