6,936 research outputs found

    A solution of a problem of Sophus Lie: Normal forms of 2-dim metrics admitting two projective vector fields

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    We give a complete list of normal forms for the 2-dimensional metrics that admit a transitive Lie pseudogroup of geodesic-preserving transformations and we show that these normal forms are mutually non-isometric. This solves a problem posed by Sophus Lie.Comment: This is an extended version of the paper that will appear in Math. Annalen. Some typos were corrected, references were updated, title was changed (as in the journal version). 31 page

    Nonexistence of an integral of the 6th degree in momenta for the Zipoy-Voorhees metric

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    We prove nonexistence of a nontrivial integral that is polynomial in momenta of degree less than 7 for the Zipoy-Voorhees spacetime with the parameter δ=2\delta=2Comment: 7 pages, no figure

    Spectral functions of strongly interacting isospin-1/2 bosons in one dimension

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    We study a system of one-dimensional (iso)spin-1/2 bosons in the regime of strong repulsive interactions. We argue that the low-energy spectrum of the system consists of acoustic density waves and the spin excitations described by an effective ferromagnetic spin chain with a small exchange constant J. We use this description to compute the dynamic spin structure factor and the spectral functions of the system.Comment: reference adde

    Zeros of the Partition Function for Higher--Spin 2D Ising Models

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    We present calculations of the complex-temperature zeros of the partition functions for 2D Ising models on the square lattice with spin s=1s=1, 3/2, and 2. These give insight into complex-temperature phase diagrams of these models in the thermodynamic limit. Support is adduced for a conjecture that all divergences of the magnetisation occur at endpoints of arcs of zeros protruding into the FM phase. We conjecture that there are 4[s2]24[s^2]-2 such arcs for s1s \ge 1, where [x][x] denotes the integral part of xx.Comment: 8 pages, latex, 3 uuencoded figure

    Coherent description of the intrinsic and extrinsic anomalous Hall effect in disordered alloys on an abab initioinitio level

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    A coherent description of the anomalous Hall effect (AHE) is presented that is applicable to pure as well as disordered alloy systems by treating all sources of the AHE on equal footing. This is achieved by an implementation of the Kubo-St\v{r}eda equation using the fully relativistic Korringa-Kohn-Rostoker (KKR) Green's function method in combination with the Coherent Potential Approximation (CPA) alloy theory. Applications to the pure elemental ferromagnets bcc-Fe and fcc-Ni led to results in full accordance with previous work. For the alloy systems fcc-Fex_xPd1x_{1-x} and fcc-Nix_xPd1x_{1-x} very satisfying agreement with experiment could be achieved for the anomalous Hall conductivity (AHC) over the whole range of concentration. To interpret these results an extension of the definition for the intrinsic AHC is suggested. Plotting the corresponding extrinsic AHC versus the longitudinal conductivity a linear relation is found in the dilute regimes, that allows a detailed discussion of the role of the skew and side-jump scattering processes.Comment: * shortened manuscript * slight rewordings * changed line style in Fig 1 * corrected misprinted S (skewness) factor * merged Fig. 3 with Fig. 1 * new citation introduce

    Coulomb Blockade with Dispersive Interfaces

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    What quantity controls the Coulomb blockade oscillations if the dot--lead conductance is essentially frequency--dependent ? We argue that it is the ac dissipative conductance at the frequency given by the effective charging energy. The latter may be very different from the bare charging energy due to the interface--induced capacitance (or inductance). These observations are supported by a number of examples, considered from the weak and strong coupling (perturbation theory vs. instanton calculus) perspectives.Comment: 4 page

    Institute of public service in russia and foreign countries: history of establishment and its modern characteristics

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    This paper analyzed the history of establishment, the features of the current institute of public service in Russia and foreign countrie

    The Yang Lee Edge Singularity on Feynman Diagrams

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    We investigate the Yang-Lee edge singularity on non-planar random graphs, which we consider as the Feynman Diagrams of various d=0 field theories, in order to determine the value of the edge exponent. We consider the hard dimer model on phi3 and phi4 random graphs to test the universality of the exponent with respect to coordination number, and the Ising model in an external field to test its temperature independence. The results here for generic (``thin'') random graphs provide an interesting counterpoint to the discussion by Staudacher of these models on planar random graphs.Comment: LaTeX, 6 pages + 3 figure
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