Energy spectrum and phase diagrams of two-sublattice hard-core boson model

The energy spectrum, spectral density and phase diagrams have been obtained for two-sublattice hard-core boson model in frames of random phase approximation approach. Reconstruction of boson spectrum at the change of temperature, chemical potential and energy difference between local positions in sublattices is studied. The phase diagrams illustrating the regions of existence of a normal phase which can be close to Mott-insulator (MI) or charge-density (CDW) phases as well as the phase with the Bose-Einstein condensate (SF phase) are built.Comment: 9 pages, 4 figure

Optical Color Gradients in Star-Forming Ring Galaxies

We compute radial color gradients produced by an outwardly propagating circular wave of star formation and compare our results with color gradients observed in the classical ring galaxy, the ``Cartwheel''. We invoke two independent models of star formation in the ring galaxies. The first one is the conventional density wave scenario, in which an intruder galaxy creates a radially propagating density wave accompanied by an enhanced star formation following the Schmidt law. The second scenario is a pure self-propagating star formation model, in which the intruder only sets off the first burst of stars at the point of impact. Both models give essentially the same results. Systematic reddening of B-V, V-K colors towards the center, such as that observed in the Cartwheel, can be obtained only if the abundance of heavy elements in the star-forming gas is a few times below solar. The B-V and V-K color gradients observed in the Cartwheel can be explained as a result of mixing of stellar populations born in a star-forming wave propagating through a low-metallicity gaseous disk, and a pre-existing stellar disk of the size of the gaseous disk with color properties typical to those observed in nearby disk galaxies.Comment: 16 pages, 12 figures; accepted for publication in the Astrophysical Journa

Ferromagnetic Detectors of Axions in RF (S - X) Band

The (pseudo) Goldstone bosons arise naturally in many modern theories such as supergravity, superstring theory and variants of general relativity with torsion. By the other hand, there are well known indications that a large part of the Universe mass exists in a form of dark matter. The most attractive model of the dark matter is non-relativistic gas of the light elementary particles weakly interacting with the "usual" matter \cite{b2} - \cite{b4}. We describe ferromagnetic detectors, for search of arion(axion), where a high-sensitive two-channel SHF receiver is used. Its sensitivity reaches to $10^{-20}\,Wt$, with time of accumulation $1-10\,s$. Fourier analysis of signal provides a survey in zone up to $\pm50\,KHz$ with spectral resolution $0.1 - 25\, Hz$. There was applied a high sensitive SHF receiver based on a special computer method of coherent accumulation of signals. It is possible to use the receiver in other precise experiments: measuring of electron/positron beams polarization in storage rings, investigation of parity violation, investigation of atmosphere with radars etc.Comment: 6 pages, LaTeX, no figure

Modernization of cathode assemblies of electron sources based on low pressure arc discharge

The paper presents modified cathode assemblies, including their main characteristics, for plasma electron sources based on a constricted low-pressure arc initiated by a discharge in crossed electric and magnetic fields. One of the modified cathode assemblies allows the electrode system of the auxiliary discharge to operate at a pressure of≈0.3 Pa, as against ≈ 10 Pa before the modification, provides a larger diameter constriction of the pulsed (up to [tau]=250 [mu]s) arc, and thus extends the range of operating currents for the plasma-cathode discharge system up to I[d]=300 A. The other modified assembly operates at widely varying discharge currents I[d]=5-100 A, provides lesser amounts of cathode microdroplets at the discharge electrodes, and allows the arc to operate at comparatively low voltages. The use of cathode assemblies adapted for specific discharge systems extends the capabilities of plasma- emitter electron sources as well as the range of their applications in scientific and technological fields

Ekaterinburg (Sverdlovsk) During NEP Years: Organization of City Government System

The article discusses the activities of various levels of government structures (city council, gubernatorial, district and regional executive and party bodies) in managing EkaterinburgSverdlovsk during the NEP years. It is established that during this period, the central government was faced with a choice between centralism or decentralization in local governance and the delineation of powers between councils and different levels of regional government. It is noted that in practice, a multilevel system of city management was formed, which had both positive and negative aspects. It is shown that on the one hand, in conditions of weak city authority and a shortage of city budget, the intervention of regional authorities in urban issues and financial injections from their side allowed for the successful resolution of acute urban economic issues. On the other hand, such a system of power significantly limited the authority of the city council, pushing it to other government structures. As a result, the author concludes that the city council was not a full-fledged, independent administrative unit, and its competence in managing the city was significantly limited. This situation is explained by the fact that the main decisions regarding the directions of city development were made by regional authorities, which did not always positively affect the effectiveness of urban management