8,941 research outputs found
Effect of disorder outside the CuO planes on of copper oxide superconductors
The effect of disorder on the superconducting transition temperature
of cuprate superconductors is examined. Disorder is introduced into the cation
sites in the plane adjacent to the CuO planes of two single-layer
systems, BiSrLnCuO and
LaNdSrCuO. Disorder is controlled by changing
rare earth (Ln) ions with different ionic radius in the former, and by varying
the Nd content in the latter with the doped carrier density kept constant. We
show that this type of disorder works as weak scatterers in contrast to the
in-plane disorder produced by Zn, but remarkably reduces suggesting
novel effects of disorder on high- superconductivity.Comment: 5 pages, 5 figures, to be published in Phys. Rev. Let
Generation of Curvature Perturbations with Extra Anisotropic Stress
We study the evolution of curvature perturbations and the cosmic microwave
background (CMB) power spectrum in the presence of an hypothesized extra
anisotropic stress which might arise, for example, from the dark radiation term
in brane-world cosmology. We evolve the scalar modes of such perturbations
before and after neutrino decoupling and analyze their effects on the CMB
spectrum. A novel result of this work is that the cancellation of the neutrino
and extra anisotropic stress could lead to a spectrum of residual curvature
perturbations which is similar to the observed CMB power spectrum. This implies
a possible additional consideration in the determination of cosmological
parameters from the CMB analysis.Comment: 13 pages, 2 figures; improved discussio
Difference equations for the higher rank XXZ model with a boundary
The higher rank analogue of the XXZ model with a boundary is considered on
the basis of the vertex operator approach. We derive difference equations of
the quantum Knizhnik-Zamolodchikov type for 2N-point correlations of the model.
We present infinite product formulae of two point functions with free boundary
condition by solving those difference equations with N=1.Comment: LaTEX 16 page
Tracking heliospheric disturbances by interplanetary scintillation
International audienceCoronal mass ejections are known as a solar cause of significant geospace disturbances, and a fuller elucidation of their physical properties and propagation dynamics is needed for space weather predictions. The scintillation of cosmic radio sources caused by turbulence in the solar wind (interplanetary scintillation; IPS) serves as an effective ground-based method for monitoring disturbances in the heliosphere. We studied global properties of transient solar wind streams driven by CMEs using 327-MHz IPS observations of the Solar-Terrestrial Environment Laboratory (STEL) of Nagoya University. In this study, we reconstructed three-dimensional features of the interplanetary (IP) counterpart of the CME from the IPS data by applying the model fitting technique. As a result, loop-shaped density enhancements were deduced for some CME events, whereas shell-shaped high-density regions were observed for the other events. In addition, CME speeds were found to evolve significantly during the propagation between the corona and 1 AU
Tidal effects on magnetic gyration of a charged particle in Fermi coordinates
We examine the gyration motion of a charged particle, viewed from a reference
observer falling along the Z axis into a Schwarzschild black hole. It is
assumed that the magnetic field is constant and uniform along the Z axis, and
that the particle has a circular orbit in the X-Y plane far from the
gravitational source. When the particle as well as the reference observer
approaches the black hole, its orbit is disrupted by the tidal force. The final
plunging velocity increases in the non-relativistic case, but decreases if the
initial circular velocity exceeds a critical value, which is approximately
0.7c. This toy model suggests that disruption of a rapidly rotating star due to
a velocity-dependent tidal force may be quite different from that of a
non-relativistic star. The model also suggested that collapse of the orbit
after the disruption is slow in general, so that the particle subsequently
escapes outside the valid Fermi coordinates.Comment: 10 pages, 12 figure
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