9,306 research outputs found
Volume estimates for equiangular hyperbolic Coxeter polyhedra
An equiangular hyperbolic Coxeter polyhedron is a hyperbolic polyhedron where
all dihedral angles are equal to \pi/n for some fixed integer n at least 2. It
is a consequence of Andreev's theorem that either n=3 and the polyhedron has
all ideal vertices or that n=2. Volume estimates are given for all equiangular
hyperbolic Coxeter polyhedra.Comment: 27 pages, 11 figures; corrected typo in Theorem 2.
Josephson Currents in Quantum Hall Devices
We consider a simple model for an SNS Josephson junction in which the "normal
metal" is a section of a filling-factor integer quantum-Hall edge. We
provide analytic expressions for the current/phase relations to all orders in
the coupling between the superconductor and the quantum Hall edge modes, and
for all temperatures. Our conclusions are consistent with the earlier
perturbative study by Ma and Zyuzin [Europhysics Letters {\bf 21} 941-945
(1993)]: The Josephson current is independent of the distance between the
superconducting leads, and the upper bound on the maximum Josephson current is
inversely proportional to the perimeter of the Hall device.Comment: Revtex4. 22 pages 9 figures. Replaced version has minor typos fixed
and one added referenc
Semiclassical Approach to Competing Orders in Two-leg Spin Ladder with Ring-Exchange
We investigate the competition between different orders in the two-leg spin
ladder with a ring-exchange interaction by means of a bosonic approach. The
latter is defined in terms of spin-1 hardcore bosons which treat the N\'eel and
vector chirality order parameters on an equal footing. A semiclassical approach
of the resulting model describes the phases of the two-leg spin ladder with a
ring-exchange. In particular, we derive the low-energy effective actions which
govern the physical properties of the rung-singlet and dominant vector
chirality phases. As a by-product of our approach, we reveal the mutual
induction phenomenon between spin and chirality with, for instance, the
emergence of a vector-chirality phase from the application of a magnetic field
in bilayer systems coupled by four-spin exchange interactions.Comment: 15 pages, 9 figure
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