1,050 research outputs found
Evolution of the vorticity-area density during the formation of coherent structures in two-dimensional flows
It is shown: 1) that in two-dimensional, incompressible, viscous flows the
vorticity-area distribution evolves according to an advection-diffusion
equation with a negative, time dependent diffusion coefficient and 2) how to
use the vorticity-streamfunction relations, i.e., the so-called scatter-plots,
of the quasi-stationary coherent structures in order to quantify the
experimentally observed changes of the vorticity distribution moments leading
to the formation of these structures.Comment: LaTeX, 15 pp., 2 eps figures. Some sections have been rewritten;
referees' Comments have been include
Simulating core excitation in breakup reactions of halo nuclei using an effective three-body force
We extend our previous calculation of the breakup of 11Be using Halo
Effective Field Theory and the Dynamical Eikonal Approximation to include an
effective 10Be-n-target force. The force is constructed to account for the
virtual excitation of 10Be to its low-lying 2+ excited state. In the case of
breakup on a 12C target this improves the description of the neutron-energy and
angular spectra, especially in the vicinity of the 11Be 5/2+ state. By
fine-tuning the range parameters of the three-body force, a reasonable
description of data in the region of the 3/2+ 11Be state can also be obtained.
This sensitivity to its range results from the structure of the overlap
integral that governs the 11Be s-to-d-state transitions induced by the
three-body force.Comment: 8 pages, 4 figure
Spin Chains as Perfect Quantum State Mirrors
Quantum information transfer is an important part of quantum information
processing. Several proposals for quantum information transfer along linear
arrays of nearest-neighbor coupled qubits or spins were made recently. Perfect
transfer was shown to exist in two models with specifically designed strongly
inhomogeneous couplings. We show that perfect transfer occurs in an entire
class of chains, including systems whose nearest-neighbor couplings vary only
weakly along the chain. The key to these observations is the Jordan-Wigner
mapping of spins to noninteracting lattice fermions which display perfectly
periodic dynamics if the single-particle energy spectrum is appropriate. After
a half-period of that dynamics any state is transformed into its mirror image
with respect to the center of the chain. The absence of fermion interactions
preserves these features at arbitrary temperature and allows for the transfer
of nontrivially entangled states of several spins or qubits.Comment: Abstract extended, introduction shortened, some clarifications in the
text, one new reference. Accepted by Phys. Rev. A (Rapid Communications
Switching dynamics between metastable ordered magnetic state and nonmagnetic ground state - A possible mechanism for photoinduced ferromagnetism -
By studying the dynamics of the metastable magnetization of a statistical
mechanical model we propose a switching mechanism of photoinduced
magnetization. The equilibrium and nonequilibrium properties of the Blume-Capel
(BC) model, which is a typical model exhibiting metastability, are studied by
mean field theory and Monte Carlo simulation. We demonstrate reversible changes
of magnetization in a sequence of changes of system parameters, which would
model the reversible photoinduced magnetization. Implications of the calculated
results are discussed in relation to the recent experimental results for
prussian blue analogs.Comment: 12 pages, 13 figure
Interaction and thermodynamics of spinons in the XX chain
The mapping between the fermion and spinon compositions of eigenstates in the
one-dimensional spin-1/2 XX model on a lattice with N sites is used to describe
the spinon interaction from two different perspectives: (i) For finite N the
energy of all eigenstates is expressed as a function of spinon momenta and
spinon spins, which, in turn, are solutions of a set of Bethe ansatz equations.
The latter are the basis of an exact thermodynamic analysis in the spinon
representation of the XX model. (ii) For N -> infinity the energy per site of
spinon configurations involving any number of spinon orbitals is expressed as a
function of reduced variables representing momentum, filling, and magnetization
of each orbital. The spins of spinons in a single orbital are found to be
coupled in a manner well described by an Ising-like equivalent-neighbor
interaction, switching from ferromagnetic to antiferromagnetic as the filling
exceeds a critical level. Comparisons are made with results for the
Haldane-Shastry model.Comment: 16 pages, 3 figure
Random-cluster representation of the Blume-Capel model
The so-called diluted-random-cluster model may be viewed as a random-cluster
representation of the Blume--Capel model. It has three parameters, a vertex
parameter , an edge parameter , and a cluster weighting factor .
Stochastic comparisons of measures are developed for the `vertex marginal' when
, and the `edge marginal' when q\in[1,\oo). Taken in conjunction
with arguments used earlier for the random-cluster model, these permit a
rigorous study of part of the phase diagram of the Blume--Capel model
Solutions of Adler's lattice equation associated with 2-cycles of the Backlund transformation
The BT of Adler's lattice equation is inherent in the equation itself by
virtue of its multidimensional consistency. We refer to a solution of the
equation that is related to itself by the composition of two BTs (with
different Backlund parameters) as a 2-cycle of the BT. In this article we will
show that such solutions are associated with a commuting one-parameter family
of rank-2 (i.e., 2-variable), 2-valued mappings. We will construct the explicit
solution of the mappings within this family and hence give the solutions of
Adler's equation that are 2-cycles of the BT.Comment: 10 pages, contribution to the NEEDS 2007 proceeding
Construction of Integrals of Higher-Order Mappings
We find that certain higher-order mappings arise as reductions of the
integrable discrete A-type KP (AKP) and B-type KP (BKP) equations. We find
conservation laws for the AKP and BKP equations, then we use these conservation
laws to derive integrals of the associated reduced maps.Comment: appear to Journal of the Physical Society of Japa
On a two-parameter extension of the lattice KdV system associated with an elliptic curve
A general structure is developed from which a system of integrable partial
difference equations is derived generalising the lattice KdV equation. The
construction is based on an infinite matrix scheme with as key ingredient a
(formal) elliptic Cauchy kernel. The consistency and integrability of the
lattice system is discussed as well as special solutions and associated
continuum equations.Comment: Submitted to the proceedings of the Oeresund PDE-symposium, 23-25 May
2002; 17 pages LaTeX, style-file include
- …