316 research outputs found
Comment on "Transverse Force on a Quantized Vortex in a Superfluid"
The result of Thouless, Ao and Niu (TAN), that the mutual friction parameter
, contradicts to the experiments made in rotating 3He-B by
Manchester group. The Manchester group observed that at low
temperature and approaches 1 at high temperature. The reason of the
contradiction is that TAN did not take into account the Iordanskii force on the
vortex and the spectral flow force, which comes from the anomaly related to the
low-energy bound states of fermions in cores of quantized vortices. The
Iordanskii force is responsible for the negative at low
temperature, while due to the spectral flow approaches 1 at high
temperature. Relation of the spectral flow anomaly with the paradoxes of the
linear and angular momenta in gapless superfluids is discussed.Comment: revtex, 2 pages, submitted to Physical Review Letters as "Comment" to
the paper D.J. Thouless, P. Ao and Q. Niu, Phys. Rev. Lett. 76, 3758 (1996
Superfluid Spin-down, with Random Unpinning of the Vortices
The so-called ``creeping'' motion of the pinned vortices in a rotating
superfluid involves ``random unpinning'' and ``vortex motion'' as two
physically separate processes. We argue that such a creeping motion of the
vortices need not be (biased) in the direction of an existing radial Magnus
force, nor should a constant microscopic radial velocity be assigned to the
vortex motion, in contradiction with the basic assumptions of the ``vortex
creep'' model. We point out internal inconsistencies in the predictions of this
model which arise due to this unjustified foundation that ignores the role of
the actual torque on the superfluid. The proper spin-down rate of a pinned
superfluid is then calculated and turns out to be much less than that suggested
in the vortex creep model, hence being of even less observational significance
for its possible application in explaining the post-glitch relaxations of the
radio pulsars.Comment: To be published in J. Low Temp. Phys., Vol. 139, May 2005 [Eqs 11,
15-17 here, have been revised and, may be substituted for the corresponding
ones in that paper
Quantum vortices in systems obeying a generalized exclusion principle
The paper deals with a planar particle system obeying a generalized exclusion
principle (EP) and governed, in the mean field approximation, by a nonlinear
Schroedinger equation. We show that the EP involves a mathematically simple and
physically transparent mechanism, which allows the genesis of quantum vortices
in the system. We obtain in a closed form the shape of the vortices and
investigate its main physical properties.
PACS numbers: 03.65.-w, 03.65.Ge, 05.45.YvComment: 7 pages, 4 figure
Evidence for microtubule subunit addition to the distal end of mitotic structures in vitro.
Internal avalanches in a pile of superconducting vortices
Using an array of miniature Hall probes, we monitored the spatiotemporal
variation of the internal magnetic induction in a superconducting niobium
sample during a slow sweep of external magnetic field. We found that a sizable
fraction of the increase in the local vortex population occurs in abrupt jumps.
The size distribution of these avalanches presents a power-law collapse on a
limited range. In contrast, at low temperatures and low fields, huge avalanches
with a typical size occur and the system does not display a well-defined
macroscopic critical current.Comment: 5 pages including 5 figure
Theory of "ferrisuperconductivity" in
We construct a two component Ginzburg-Landau theory with coherent pair motion
and incoherent quasiparticles for the phase diagram of .
The two staggered superconducting states live at the Brillouin zone center and
the zone boundary, and coexist for temperatures at concentrations
. We predict below
appearance of a charge density wave (CDW) and Be-sublattice distortion. The
distortion explains the SR relaxation anomaly, and Th-impurity mediated
scattering of ultrasound to CDW fluctuations explains the attenuation peak.Comment: 4 pages, 4 eps figures, REVTe
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