245 research outputs found

    Vector Field and Inflation

    Full text link
    We have investigated if the vector field can give rise to an accelerating phase in the early universe. We consider a timelike vector field with a general quadratic kinetic term in order to preserve an isotropic background spacetime. The vector field potential is required to satisfy the three minimal conditions for successful inflation: i) ρ>0\rho>0, ii) ρ+3P<0\rho+3P < 0 and iii) the slow-roll conditions. As an example, we consider the massive vector potential and small field type potential as like in scalar driven inflation.Comment: 1+7pages, 3figures, To appear in the Proceedings of the CospA 2008, Kore

    Dirac quantization of free motion on curved surfaces

    Full text link
    We give an explicit operator realization of Dirac quantization of free particle motion on a surface of codimension 1. It is shown that the Dirac recipe is ambiguous and a natural way of fixing this problem is proposed. We also introduce a modification of Dirac procedure which yields zero quantum potential. Some problems of abelian conversion quantization are pointed out.Comment: 16 page

    Inflation driven by scalar field with non-minimal kinetic coupling with Higgs and quadratic potentials

    Full text link
    We study a scalar field with non-minimal kinetic coupling to itself and to the curvature. The slow rolling conditions allowing an inflationary background have been found. The quadratic and Higgs type potentials have been considered, and the corresponding values for the scalar fields at the end of inflation allows to recover the connection with particle physics.Comment: 16 pages, to appear in JCA

    Discovering the Far East...’: Images of the Territory in the Works of V. K. Arsenyev

    Get PDF
    The article explores the works of the Far East explorer V.K. Arsenyev (1872–1930) with the purpose of using his works to find the representational potential of the region’s image. Using social constructivism as a methodology, we outline and analyze scientific and artistic types of constructing the Far East image and demonstrate the place each of these types occupies in Arsenyev’s works. &nbsp; &nbsp; Keywords: regional image, constructivism, construct, visualization, Russian Far East, V.K.Arsenye

    A live border: cossack maneuvers in the context of colonization (the late sixteenth to the early seventeenth century) = Живая граница: казачьи маневры в пространстве колонизации (рубеж XVI-XVII вв.)

    Get PDF
    The Cossacks personified a "live border" in the southern Russian periphery (Ukraina), one that maneuvered between the Muscovite state, the Polish-Lithuanian Commonwealth, the Crimean Khanate, and the Nogai Hord

    Gravitational Waves in New General Relativity

    Full text link
    The models of New General Relativity have recently got attention of research community, and there are some works studying their dynamical properties. The formal aspects of this investigation have been mostly restricted to the primary constraints in the Hamiltonian analysis. However, it is by far not enough for counting their degrees of freedom or judging whether they are any good and viable. In this paper we study linearised equations in vacuum around the trivial Minkowski tetrad. By taking the approach of cosmological perturbation theory we show that the numbers of primary constraints are very easily seen without any need of genuine Hamiltonian techniques, and give the full count of linearised degrees of freedom in the weak field limit of each and every version of New General Relativity without matter.Comment: 14 page

    The Arctic in the Soviet cinema lens: “Two Oceans” by Vladimir Shneiderov

    Get PDF
    The study aims at introducing unstudied materials, i.e., film documents of the Soviet period, related to the development of the Russian North, into the scientific circulation. So-called expedition films occupied a special place in the history of Soviet visual anthropology — films of educational content about the peoples and territories of the USSR. They reached its heyday at the turn of the 1920s — 1930s. One of the pioneers of Soviet visual anthropology is considered to be the filmmaker V.A. Shneiderov, the author of a series of films about the USSR territories (“The Great Flight”, “The Pamirs (the bottom of death)”, “At the height of 4500”, etc.). In addition to solving creative issues, the production of such films was part of a state experiment on the construction of local images and the country. The Soviet authorities used the resources of the cinematographer as a media source and agitation. In this article, the author considers the example of the expedition film “Two Oceans”, the classic of documentary films where V.A. Shneiderov pictured the history of the Northern Sea Route and the Soviet colonization of the Arctic. The context of the filmmaking, i.e., parallel processes in Soviet cultural politics and cinema, is discussed as well. The author conclusions contain thoughts about the research value of the Soviet expeditionary film as a complex historical source

    Non-gaussianity from the trispectrum and vector field perturbations

    Get PDF
    We use the \delta N formalism to study the trispectrum T_\zeta of the primordial curvature perturbation \zeta when the latter is generated by vector field perturbations, considering the tree-level and one-loop contributions. The order of magnitude of the level of non-gaussianity in the trispectrum, \tau_{NL}, is calculated in this scenario and related to the order of magnitude of the level of non-gaussianity in the bispectrum, f_{NL}, and the level of statistical anisotropy in the power spectrum, g_\zeta. Such consistency relations will put under test this scenario against future observations. Comparison with the expected observational bound on \tau_{NL} from WMAP, for generic inflationary models, is done.Comment: LaTeX file, 12 pages, no figures. v2: Minor changes, conclusions unchanged. v3: Version accepted for publication in Physics Letters

    On the Limits of Gate Elimination

    Get PDF
    Although a simple counting argument shows the existence of Boolean functions of exponential circuit complexity, proving superlinear circuit lower bounds for explicit functions seems to be out of reach of the current techniques. There has been a (very slow) progress in proving linear lower bounds with the latest record of 3 1/86*n-o(n). All known lower bounds are based on the so-called gate elimination technique. A typical gate elimination argument shows that it is possible to eliminate several gates from an optimal circuit by making one or several substitutions to the input variables and repeats this inductively. In this note we prove that this method cannot achieve linear bounds of cn beyond a certain constant c, where c depends only on the number of substitutions made at a single step of the induction
    corecore