301 research outputs found
Self-Consistent Mean-Field Theory for Frustrated Josephson Junction Arrays
We review the self-consistent mean-field theory for charge-frustrated
Josephson junction arrays. Using (\phi is the phase of the
superconducting wavefunction) as order parameter and imposing the
self-consistency condition, we compute the phase boundary line between the
superconducting region ( not equal to zero) and the insulating one
( = 0). For a uniform offset charge q=e the superconducting phase
increases with respect to the situation in which q=0. Here, we generalize the
self-consistent mean-field theory to include the effects induced by a random
distribution of offset charges and/or of diagonal self-capacitances. For most
of the phase diagram, our results agree with the outcomes of Quantum Monte
Carlo simulations as well as with previous studies using the path-integral
approach.Comment: Presented by F. P. Mancini at the Conference "Highlights in Condensed
Matter Physics", May 9-11 2003, Salerno, Ital
Superconducting Topological Fluids in Josephson Junction Arrays
We argue that the frustrated Josephson junction arrays may support a
topologically ordered superconducting ground state, characterized by a
non-trivial ground state degeneracy on the torus. This superconducting quantum
fluid provides an explicit example of a system in which superconductivity
arises from a topological mechanism rather than from the usual Landau-Ginzburg
mechanism.Comment: 4 page
Topology Induced Spatial Bose-Einstein Condensation for Bosons on Star-Shaped Optical Networks
New coherent states may be induced by pertinently engineering the topology of
a network. As an example, we consider the properties of non-interacting bosons
on a star network, which may be realized with a dilute atomic gas in a
star-shaped deep optical lattice. The ground state is localized around the star
center and it is macroscopically occupied below the Bose-Einstein condensation
temperature T_c. We show that T_c depends only on the number of the star arms
and on the Josephson energy of the bosonic Josephson junctions and that the
non-condensate fraction is simply given by the reduced temperature T/T_c.Comment: 20 Pages, 5 Figure
Solitary Waves and Compactons in a class of Generalized Korteweg-DeVries Equations
We study the class of generalized Korteweg-DeVries equations derivable from
the Lagrangian: L(l,p) = \int \left( \frac{1}{2} \vp_{x} \vp_{t} - {
{(\vp_{x})^{l}} \over {l(l-1)}} + \alpha(\vp_{x})^{p} (\vp_{xx})^{2} \right)
dx, where the usual fields of the generalized KdV equation are
defined by u(x,t) = \vp_{x}(x,t). This class contains compactons, which are
solitary waves with compact support, and when , these solutions have the
feature that their width is independent of the amplitude. We consider the
Hamiltonian structure and integrability properties of this class of KdV
equations. We show that many of the properties of the solitary waves and
compactons are easily obtained using a variational method based on the
principle of least action. Using a class of trial variational functions of the
form we
find soliton-like solutions for all , moving with fixed shape and constant
velocity, . We show that the velocity, mass, and energy of the variational
travelling wave solutions are related by , where , independent of .\newline \newline PACS numbers: 03.40.Kf,
47.20.Ky, Nb, 52.35.SbComment: 16 pages. LaTeX. Figures available upon request (Postscript or hard
copy
Lattice Gauge Theories and the Heisenberg Antiferromagnetic Chain
We study the strongly coupled 2-flavor lattice Schwinger model and the
SU(2)-color QCD_2. The strong coupling limit, even with its inherent
nonuniversality, makes accurate predictions of the spectrum of the continuum
models and provides an intuitive picture of the gauge theory vacuum. The
massive excitations of the gauge model are computable in terms of spin-spin
correlators of the quantum Heisenberg antiferromagnetic spin-1/2 chain.Comment: Proceedings LATTICE99 (spin models), 3 page
Finite-temperature corrections to the Lorenz ratio at the N = 3 topological Kondo fixed point
We analyze the finite-temperature scaling of the Lorenz ratio at the topological Kondo fixed point realized at a junction of three interacting quantum wires connected to a floating superconducting island. Using the Tomonaga-Luttinger liquid approach to the quantum wires, we derive the full functional dependence of the finite-temperature correction on the Luttinger parameter g
Propagation of Discrete Solitons in Inhomogeneous Networks
In many physical applications solitons propagate on supports whose
topological properties may induce new and interesting effects. In this paper,
we investigate the propagation of solitons on chains with a topological
inhomogeneity generated by the insertion of a finite discrete network on the
chain. For networks connected by a link to a single site of the chain, we
derive a general criterion yielding the momenta for perfect reflection and
transmission of traveling solitons and we discuss solitonic motion on chains
with topological inhomogeneities
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