Bose-Einstein Condensates in Strongly Disordered Traps

A Bose-Einstein condensate in an external potential consisting of a superposition of a harmonic and a random potential is considered theoretically. From a semi-quantitative analysis we find the size, shape and excitation energy as a function of the disorder strength. For positive scattering length and sufficiently strong disorder the condensate decays into fragments each of the size of the Larkin length ${\cal L}$. This state is stable over a large range of particle numbers. The frequency of the breathing mode scales as $1/{\cal L}^2$. For negative scattering length a condensate of size ${\cal L}$ may exist as a metastable state. These finding are generalized to anisotropic traps

Localized states and interaction induced delocalization in Bose gases with quenched disorder

Very diluted Bose gas placed into a disordered environment falls into a fragmented localized state. At some critical density the repulsion between particles overcomes the disorder. The gas transits into a coherent superfluid state. In this article the geometrical and energetic characteristics of the localized state at zero temperature and the critical density at which the quantum phase transition from the localized to the superfluid state proceeds are found.Comment: 17 pages, 5 figur

Hydrogeochemical characteristics of water intakes from groundwater sources in Seversk

The article describes the hydrogeochemical environment behavior analysis of groundwater intake which, in its turn. provides the utility and drinking water supply for Seversk. The reasons for temporary changes of the hydrogeochemical aquifer indicators in the producing areas have been highlighted. The main factor could be upset hydrodynamic conditions during long-term operation. Changed hydrogeochemical indicators have been revealed not only during the technological water treatment process but also during water transportation to consumers. Chemical composition water changes are related to secondary mineral and sludge formation on technological equipment. Precipitation is a polymineral mixture predominantly a ferrous phase. whereas phosphate and carbonate phases are secondary. Clay minerals are also found

Spin Resonance and dc Current Generation in a Quantum Wire

We show that in a quantum wire the spin-orbit interaction leads to a narrow spin resonance at low temperatures, even in the absence of an external magnetic field. Resonance absorption by linearly polarized radiation gives a dc spin current; resonance absorption by circularly polarized radiation gives a dc electric current or magnetization

Развитие технологий пластического формообразования металлов с использованием промежуточных сред (гидродинамическое выдавливание, гидроударная штамповка)

Development of metal forming technologies with the use of fluid or pseudo-fluid media in application to difficult-to-deform and low-plastic materials is described. Two technological directions are considered: (i) hot hydrodynamic extrusion of cast iron articles using electrode graphite as a pseudo-fluid medium, and (ii) cold impact hydroforming of sheet materials using a liquid (a machining emulsion) and pseudo-fluid (polyurethane) medium. The most important achievements of the Physical Technical Institute in both of these directions and their advantages are described.Описаны технологии пластического формообразования металлов с использованием жидких и псевдожидких сред применительно к труднодеформируемым, малопластичным и труднообрабатываемым материалам, разработанные в Физико-техническом институте НАН Беларуси. Рассмотрены два технологических направления: 1) горячее гидродинамическое выдавливание изделий из чугуна с применением в качестве квазижидкой среды электродного графита, 2) холодная импульсная гидроударная штамповка листовых материалов с использованием жидких (станочная эмульсия) и псевдожидких (полиуретан) сред. Показаны преимущества каждого из направлений и представлены результаты наиболее значимых достижений института в данных областях за последние годы

Interacting Electrons on a Square Fermi Surface

Electronic states near a square Fermi surface are mapped onto quantum chains. Using boson-fermion duality on the chains, the bosonic part of the interaction is isolated and diagonalized. These interactions destroy Fermi liquid behavior. Non-boson interactions are also generated by this mapping, and give rise to a new perturbation theory about the boson problem. A case with strong repulsions between parallel faces is studied and solved. There is spin-charge separation and the square Fermi surface remains square under doping. At half-filling, there is a charge gap and insulating behavior together with gapless spin excitations. This mapping appears to be a general tool for understanding the properties of interacting electrons on a square Fermi surface.Comment: 25 pages, Nordita preprint 94/22

Geochemical groundwater peculiarities of Paleogene sediments in S-E Western Siberia artesian basin

The geochemical peculiarities of groundwater in Paleogene deposits in southeastern part of Western Siberia artesian basin are considered in the paper. Landscape, climate, geostructural and hydrogeological conditions define the water composition and quality peculiarities in this region. It has been established that ion-saline composition, mineralization and water quality changes arre governed by the horizontal zonal distribution. Groundwater of taiga landscapes generally is in equilibrium with kaolinite and quartz, mainly involving Ca- and Mg-montmorillonite, illite, carbonate minerals, sometimes barite. Groundwater in woodland grass and grassland, together with previously mentioned minerals, is usually in equilibrium with barite, colestine, and particularly, fluorite and gypsum. As a result, all relevant elements are removed from the groundwater and their accumulation level is restricted

Geochemical groundwater peculiarities of Paleogene sediments in S-E Western Siberia artesian basin

The geochemical peculiarities of groundwater in Paleogene deposits in southeastern part of Western Siberia artesian basin are considered in the paper. Landscape, climate, geostructural and hydrogeological conditions define the water composition and quality peculiarities in this region. It has been established that ion-saline composition, mineralization and water quality changes arre governed by the horizontal zonal distribution. Groundwater of taiga landscapes generally is in equilibrium with kaolinite and quartz, mainly involving Ca- and Mg-montmorillonite, illite, carbonate minerals, sometimes barite. Groundwater in woodland grass and grassland, together with previously mentioned minerals, is usually in equilibrium with barite, colestine, and particularly, fluorite and gypsum. As a result, all relevant elements are removed from the groundwater and their accumulation level is restricted

Universal mechanism of discontinuity of commensurate-incommensurate transitions in three-dimensional solids: Strain dependence of soliton self-energy

We show that there exists a universal mechanism of long-range soliton attraction in three-dimensional solids and, therefore, of discontinuity of any commensurate-incommensurate (C-IC) phase transition. This mechanism is due to the strain dependence of the soliton self-energy and specific features of the solid-state elasticity. The role of this mechanism is studied in detail for a class of C-IC transitions where the IC modulation is one-dimensional, the anisotropy in the order parameter space is small, and the symmetry of the systems allows the existence of the Lifshitz invariant. Two other mechanisms of soliton attraction are operative here but the universal mechanism considered in this paper is found to be the most important one in some cases. Comparison with the most extensively studied C-IC transition in $\rm K_2SeO_4$ shows that the experimentally observed thermal anomalies can be understood as a result of the smearing of the theoretically predicted discontinuous transition.Comment: 8 pages (extended version, title changed