Finite temperature dynamics of vortices in the two dimensional anisotropic Heisenberg model

We study the effects of finite temperature on the dynamics of non-planar vortices in the classical, two-dimensional anisotropic Heisenberg model with XY- or easy-plane symmetry. To this end, we analyze a generalized Landau-Lifshitz equation including additive white noise and Gilbert damping. Using a collective variable theory with no adjustable parameters we derive an equation of motion for the vortices with stochastic forces which are shown to represent white noise with an effective diffusion constant linearly dependent on temperature. We solve these stochastic equations of motion by means of a Green's function formalism and obtain the mean vortex trajectory and its variance. We find a non-standard time dependence for the variance of the components perpendicular to the driving force. We compare the analytical results with Langevin dynamics simulations and find a good agreement up to temperatures of the order of 25% of the Kosterlitz-Thouless transition temperature. Finally, we discuss the reasons why our approach is not appropriate for higher temperatures as well as the discreteness effects observed in the numerical simulations.

Spin degree of freedom in two dimensional exciton condensates

We present a theoretical analysis of a spin-dependent multicomponent condensate in two dimensions. The case of a condensate of resonantly photoexcited excitons having two different spin orientations is studied in detail. The energy and the chemical potentials of this system depend strongly on the spin polarization. When electrons and holes are located in two different planes, the condensate can be either totally spin polarized or spin unpolarized, a property that is measurable. The phase diagram in terms of the total density and electron-hole separation is discussed.

HIVEL2D : a two-dimensional flow model for high-velocity channels /

At head of title: "Repair, Evaluation, Maintenance, and Rehabilitation Research Program."

Application of a two-dimensional model of hydrodynamics to San Timoteo Creek flood-control channel, California /

"October 1994."

Speeding up computation in two-dimensional iterative arrays /

"UILU-ENG 80 1720."-- Cover, p. 1.

Singular solutions at boundary intersections in two dimensional quasi-linear homogeneous partial differential equations /

Includes bibliographical references (20).

Colftar: a real-time electro-optical system for two dimensional Fourier transforms /

Thesis--University of Illinois.

Two-dimensional tests of wave transmission and reflection characteristics of laboratory breakwaters /

"June 1980."

Finite-difference schemes compared for wave-deformation characteristics in mathematical modeling of two-dimensional long-wave propagation /

"October 1970."

Recirculation principle for ground effect machine two-dimensional tests.

"Task 9R99-01-005-04. Contract DA 44-177-TC-710."

ADEP, one- and two-dimensional few-group kinetics code /

"Prepared for U.S. Atomic Energy Commission under contract W-7405-eng-92."

R2D2 : a Fortran program for two-dimensional chemically reacting, hyperthermal, internal flows.

"January 1980."

Computer program and data listing for two-dimensional ground-water model for Laramie County, Wyoming /

Mode of access: Internet.

TDP : a two-dimensional perturbation calculation code based on TDC, for IBM-7090, Deck B 516 /

Work performed at CANEL.

Rules for descriptive cataloging in the Library of Congress: pictures, designs, and other two-dimensional representations.

Mode of access: Internet.