2,337 research outputs found
Phenomenological correlations in high-temperature superconductors
An interpretation of the quadratic parameter of the Ginzburg-Landau theory of
superconductivity is presented in this paper. The negative term in the
potential, which allows the spontaneous symmetry breaking, is interpreted as a
direct contribution from the energy gap at the Fermi surface to the effective
potential. As a result, in the London approximation of the Ginzburg-Landau
theory for type-II superconductors, a strong correlation is predicted and
observed between the upper critical field at zero kelvin and the critical
temperature in high temperature superconductors.Comment: 4 pages, 2 figure
Absolutely continuous spectrum for the isotropic Maxwell operator with coefficients that are periodic in some directions and decay in others
The purpose of this paper is to prove that the spectrum of an isotropic
Maxwell operator with electric permittivity and magnetic permeability that are
periodic along certain directions and tending to a constant super-exponentially
fast in the remaining directions is purely absolutely continuous. The basic
technical tools is a new ``operatorial'' identity relating the Maxwell operator
to a vector-valued Schrodinger operator. The analysis of the spectrum of that
operator is then handled using ideas developed by the same authors in a
previous paper
Image of the Burau Representation at -th Roots of unity
We prove that the image of the Full braid group on strands
under the Burau representation, evaluated at a primitive -th root of unity
is arithmetic provided .Comment: To appear in Annals of Mathematics. arXiv admin note: text overlap
with arXiv:1204.477
Deformed Fermi Surface Theory of Magneto-Acoustic Anomaly in Modulated Quantum Hall Systems Near
We introduce a new generic model of a deformed Composite Fermion-Fermi
Surface (CF-FS) for the Fractional Quantum Hall Effect near in the
presence of a periodic density modulation. Our model permits us to explain
recent Surface Acoustic Wave observations of anisotropic anomalies [1,2] in
sound velocity and attenuation- appearance of peaks and anisotropy - which
originate from contributions to the conductivity tensor due to regions of the
CF-FS which are flattened by the applied modulation. The calculated magnetic
field and wave vector dependence of the CF conductivity,velocity shift and
attenuation agree with experiments.Comment: Revised manuscript (cond-mat/9807044) 23 September 1998; 10 page
Dual generators of the fundamental group and the moduli space of flat connections
We define the dual of a set of generators of the fundamental group of an
oriented two-surface of genus with punctures and the
associated surface with a disc removed. This dual is
another set of generators related to the original generators via an involution
and has the properties of a dual graph. In particular, it provides an algebraic
prescription for determining the intersection points of a curve representing a
general element of the fundamental group with the
representatives of the generators and the order in which these intersection
points occur on the generators.We apply this dual to the moduli space of flat
connections on and show that when expressed in terms both, the
holonomies along a set of generators and their duals, the Poisson structure on
the moduli space takes a particularly simple form. Using this description of
the Poisson structure, we derive explicit expressions for the Poisson brackets
of general Wilson loop observables associated to closed, embedded curves on the
surface and determine the associated flows on phase space. We demonstrate that
the observables constructed from the pairing in the Chern-Simons action
generate of infinitesimal Dehn twists and show that the mapping class group
acts by Poisson isomorphisms.Comment: 54 pages, 13 .eps figure
Quantum Versus Mean Field Behavior of Normal Modes of a Bose-Einstein Condensate in a Magnetic Trap
Quantum evolution of a collective mode of a Bose-Einstein condensate
containing a finite number N of particles shows the phenomena of collapses and
revivals. The characteristic collapse time depends on the scattering length,
the initial amplitude of the mode and N. The corresponding time values have
been derived analytically under certain approximation and numerically for the
parabolic atomic trap. The revival of the mode at time of several seconds, as a
direct evidence of the effect, can occur, if the normal component is
significantly suppressed.
We also discuss alternative means to verify the proposed mechanism.Comment: minor corrections are introduced into the tex
Abelian subgroups of Garside groups
In this paper, we show that for every abelian subgroup of a Garside
group, some conjugate consists of ultra summit elements and the
centralizer of is a finite index subgroup of the normalizer of .
Combining with the results on translation numbers in Garside groups, we obtain
an easy proof of the algebraic flat torus theorem for Garside groups and solve
several algorithmic problems concerning abelian subgroups of Garside groups.Comment: This article replaces our earlier preprint "Stable super summit sets
in Garside groups", arXiv:math.GT/060258
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