228,130 research outputs found

    Curvature Expansion for the Gluodynamics String including Perturbative Gluonic Contributions

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    Perturbation theory in the nonperturbative QCD vacuum and the non-Abelian Stokes theorem, representing a Wilson loop in the SU(2) gluodynamics as an integral over all the orientations in colour space, are applied to a derivation of the correction to the string effective action in the lowest order in the coupling constant gg. This correction is due to the interaction of perturbative gluons with the string world sheet and affects only the coupling constant of the rigidity term, while its contribution to the string tension of the Nambu-Goto term vanishes. The obtained correction to the rigidity coupling constant multiplicatively depends on the colour "spin" of the representation of the Wilson loop under consideration and a certain path integral, which includes the background Wilson loop average.Comment: 9 pages, LaTeX, no figure

    Properties of tunnel Josephson junctions with a ferromagnetic interlayer

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    We investigate superconductor/insulator/ferromagnet/superconductor (SIFS) tunnel Josephson junctions in the dirty limit, using the quasiclassical theory. We formulate a quantitative model describing the oscillations of critical current as a function of thickness of the ferromagnetic layer and use this model to fit recent experimental data. We also calculate quantitatively the density of states (DOS) in this type of junctions and compare DOS oscillations with those of the critical current.Comment: 9 pages, 8 figures, to be published in Phys. Rev.

    Contextual approach to quantum mechanics and the theory of the fundamental prespace

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    We constructed a Hilbert space representation of a contextual Kolmogorov model. This representation is based on two fundamental observables -- in the standard quantum model these are position and momentum observables. This representation has all distinguishing features of the quantum model. Thus in spite all ``No-Go'' theorems (e.g., von Neumann, Kochen and Specker,..., Bell) we found the realist basis for quantum mechanics. Our representation is not standard model with hidden variables. In particular, this is not a reduction of quantum model to the classical one. Moreover, we see that such a reduction is even in principle impossible. This impossibility is not a consequence of a mathematical theorem but it follows from the physical structure of the model. By our model quantum states are very rough images of domains in the space of fundamental parameters - PRESPACE. Those domains represent complexes of physical conditions. By our model both classical and quantum physics describe REDUCTION of PRESPACE-INFORMATION. Quantum mechanics is not complete. In particular, there are prespace contexts which can be represented only by a so called hyperbolic quantum model. We predict violations of the Heisenberg's uncertainty principle and existence of dispersion free states.Comment: Plenary talk at Conference "Quantum Theory: Reconsideration of Foundations-2", Vaxjo, 1-6 June, 200

    Spin-orbit field switching of magnetization in ferromagnetic films with perpendicular anisotropy

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    As an alternative to conventional magnetic field, the effective spin-orbit field in transition metals, derived from the Rashba field experienced by itinerant electrons confined in a spatial inversion asymmetric plane through the s-d exchange interaction, is proposed for the manipulation of magnetization. Magnetization switching in ferromagnetic thin films with perpendicular magnetocrystalline anisotropy can be achieved by current induced spin-orbit field, with small in-plane applied magnetic field. Spin-orbit field induced by current pulses as short as 10 ps can initiate ultrafast magnetization switching effectively, with experimentally achievable current densities. The whole switching process completes in about 100 ps.Comment: 4 pages, 3 figure
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