1,180 research outputs found

    Holomorphic Anomaly in Gauge Theory on ALE space

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    We consider four-dimensional Omega-deformed N=2 supersymmetric SU(2) gauge theory on A1 space and its lift to five dimensions. We find that the partition functions can be reproduced via special geometry and the holomorphic anomaly equation. Schwinger type integral expressions for the boundary conditions at the monopole/dyon point in moduli space are inferred. The interpretation of the five-dimensional partition function as the partition function of a refined topological string on A1x(local P1xP1) is suggested.Comment: 28 page

    Gauged Gravity via Spectral Asymptotics of non-Laplace type Operators

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    We construct invariant differential operators acting on sections of vector bundles of densities over a smooth manifold without using a Riemannian metric. The spectral invariants of such operators are invariant under both the diffeomorphisms and the gauge transformations and can be used to induce a new theory of gravitation. It can be viewed as a matrix generalization of Einstein general relativity that reproduces the standard Einstein theory in the weak deformation limit. Relations with various mathematical constructions such as Finsler geometry and Hodge-de Rham theory are discussed.Comment: Version accepted by J. High Energy Phys. Introduction and Discussion significantly expanded. References added and updated. (41 pages, LaTeX: JHEP3 class, no figures

    Superconductivity near the vibrational mode instability in MgCNi3

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    To understand the role of electron-phonon interaction in superconducting MgCNi3_{3} we have performed density functional based linear response calculations of its lattice dynamical properties. A large coupling constant λ% \lambda = 1.51 is predicted and contributing phonons are identified as displacements of Ni atoms towards octahedral interstitials of the perovskite lattice. Instabilities found for some vibrational modes emphasize the role of anharmonic effects in resolving experimental controversies.Comment: 4 pages, 4 eps figures, replaces the older versio

    Topological (Sliced) Doping of a 3D Peierls System: Predicted Structure of Doped BaBiO3

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    At hole concentrations below x=0.4, Ba_(1-x)K_xBiO_3 is non-metallic. At x=0, pure BaBiO3 is a Peierls insulator. Very dilute holes create bipolaronic point defects in the Peierls order parameter. Here we find that the Rice-Sneddon version of Peierls theory predicts that more concentrated holes should form stacking faults (two-dimensional topological defects, called slices) in the Peierls order parameter. However, the long-range Coulomb interaction, left out of the Rice-Sneddon model, destabilizes slices in favor of point bipolarons at low concentrations, leaving a window near 30% doping where the sliced state is marginally stable.Comment: 6 pages with 5 embedded postscript figure

    Self-Trapped Exciton Defects in a Charge Density Wave: Electronic Excitations of BaBiO3

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    In the previous paper, it was shown that holes doped into BaBiO3 self-trap as small polarons and bipolarons. These point defects are energetically favorable partly because they undo locally the strain in the charge-density-wave (Peierls insulator) ground state. In this paper the neutral excitations of the same model are discussed. The lowest electronic excitation is predicted to be a self-trapped exciton, consisting of an electron and a hole located on adjacent Bi atoms. This excitation has been seen experimentally (but not identified as such) via the Urbach tail in optical absorption, and the multi-phonon spectrum of the ``breathing mode'' seen in Raman scattering. These two phenomena occur because of the Franck-Condon effect associated with oxygen displacement in the excited state.Comment: 5 pages with 7 embedded figures. See also cond-mat/0108089 on polarons and bipolarons in BaBiO3 contains background informatio

    Smooth Paths on Three Dimensional Lattice

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    A particular class of random walks with a spin factor on a three dimensional cubic lattice is studied. This three dimensional random walk model is a simple generalization of random walk for the two dimensional Ising model. All critical diffusion constants and associated critical exponents are calculated. Continuum field theories such as Klein-Gordon, Dirac and massive Chern-Simons theories are constructed near several critical points.Comment: 7 pages,NUP-A-94-

    Quasiparticle contribution to heat carriers relaxation time in DyBa2_2Cu3_3O7x_{7-x} from heat diffusivity measurements

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    It is shown that the controversy on phonons or electrons being the most influenced heat carriers below the critical temperature of high-Tc_c superconductors can be resolved. Electrical and thermal properties of the same DyBa2_2Cu3_3O7x_{7-x} monodomain have been measured for two highly different oxygenation levels. While the oxygenated sample DyBa2_2Cu3_3O7_{7} has very good superconducting properties (Tc=90T_c=90 K), the DyBa2_2Cu3_3O6.3_{6.3} sample exhibits an insulator behavior. A careful comparison between measurements of the {\bf thermal diffusivity} of both samples allows us to extract the electronic contribution. This contribution to the relaxation time of heat carriers is shown to be large below TcT_c and more sensitive to the superconducting state than the phonon contribution.Comment: 13 pages, 6 figure

    Fundamental Physical Constants: Looking from Different Angles

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    We consider fundamental physical constants which are among a few of the most important pieces of information we have learned about Nature after its intensive centuries-long studies. We discuss their multifunctional role in modern physics including problems related to the art of measurement, natural and practical units, origin of the constants, their possible calculability and variability etc

    Del Pezzo surfaces of degree 1 and jacobians

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    We construct absolutely simple jacobians of non-hyperelliptic genus 4 curves, using Del Pezzo surfaces of degree 1. This paper is a natural continuation of author's paper math.AG/0405156.Comment: 24 page
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