3,824 research outputs found

    Current in narrow channels of anisotropic superconductors

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    We argue that in channels cut out of anisotropic single crystal superconductors and narrow on the scale of London penetration depth, the persistent current must cause the transverse phase difference provided the current does not point in any of the principal crystal directions. The difference is proportional to the current value and depends on the anisotropy parameter, on the current direction relative to the crystal, and on the transverse channel dimension. An experimental set up to measure the transverse phase is proposed.Comment: 3 pages, 1 figur

    The role of cosmic rays in magnetic hydrodynamics of interstellar medium

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    Cosmic ray (CR) propagation in the Galaxy and generally in the cosmic plasma is usually considered in the diffusion approximation. The diffusion is regarded to result from CR scattering due to their interaction with a magnetic and an electric field. In most cases the fields are assumed to be given. Meanwhile, in the Galaxy the CR energy density w sub cr is similar to I eV/cm, i.e., it is comparable with the energy densities of the magnetic field and turbulent motions in the interstellar gas. Therefore, for the Galaxy it becomes necessary to take into account the influence of CR on the gas dynamics and on the magnetic fields in this gas. The simplest way to this is to use the hydrodynamic approximation, but this is possible only on scales greatly exceeding the CR free path lambda before scattering and only for times larger than lambda/v approx. equals lambda/c. One should thus obtain corresponding MHD equations and establish the limits of their applicability

    On the powerful X-ray emission of radiogalaxies

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    Radio galactic emission and cosmic X-radiatio

    The role of energy-momentum conservation in emission of Cherenkov gluons

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    The famous formula for the emission angle of Cherenkov radiation should be modified when applied to hadronic reactions because of recoil effects. They impose the upper limit on the energy of the gluon emitted at a given angle. Also, it leads to essential corrections to the nuclear refractive index value as determined from the angular position of Cherenkov rings.Comment: 6

    On a Coherent Radioemission Mechanism in Quasars and in the Remains of Supernovae

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    Coherent radio emission mechanism in quasars and remains of supernova

    Finite-Size Effects in the ϕ4\phi^{4} Field Theory Above the Upper Critical Dimension

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    We demonstrate that the standard O(n) symmetric ϕ4\phi^{4} field theory does not correctly describe the leading finite-size effects near the critical point of spin systems on a dd-dimensional lattice with d>4d > 4. We show that these finite-size effects require a description in terms of a lattice Hamiltonian. For nn \to \infty and n=1n=1 explicit results are given for the susceptibility and for the Binder cumulant. They imply that recent analyses of Monte-Carlo results for the five-dimensional Ising model are not conclusive.Comment: 4 pages, latex, 1 figur

    The gravitational Vavilov-Cherenkov effect

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    In this essay we show that an uncharged black-hole moving superluminally in a transparent dielectric medium violates Hawking's area theorem. The violation is overcome through the emission of radiation. Since modes cannot emerge from the black hole itself, this radiation must originate from a collective effect in the medium, in complete analogy with the Vavilov-Cherenkov effect. However, because the black-hole is uncharged, the emission mechanism must be different. We discuss the physical origin of the effect and obtain a Newtonian estimative. Then we obtain the appropriate equations in the relativistic case and show that the field which is radiated away is a combination of gravitational and electromagnetic degrees of freedom. Possible astrophysical relevance for the detection of primordial black-holes and binary systems is discussed.Comment: 9 pages, Honorable Mention from the Gravity Research Foundation, 199

    On details of the thermodynamical derivation of the Ginsburg--Landau equations

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    We examine the procedure of thermodynamical derivation of the Ginsburg--Landau equation for current, which is given unclear and contradictory interpretations in existing textbooks. We clarify all steps of this procedure and find as a consequence a limitation on the validity range of the thermodynamic Ginsburg--Landau theory, which does not seem to be explicitely stated up to now: we conclude that the thermodynamic theory is applicable only to a superconducting specimen that is not a part of an external current-carrying loop.Comment: 11 pages. Accepted for publication in 'Superconductor Science and Technology

    On the origin of cosmic rays

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    Uniform and metagalactic cosmic ray models - halo, disk, and nonstationary galactic model
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