Vortex Lines in Three-Dimensional Magnetic Nanodots by Langevin Simulation

2018 ◽  
pp. 101-122
Author(s):  
Ph. Depondt ◽  
J.-C. S. Lévy
Keyword(s):  
Three Dimensional ◽  
Magnetic Nanodots ◽  
Vortex Lines ◽  
Langevin Simulation

Vortices in Motionless Media

1990 ◽  
Vol 43 (12) ◽  
pp. 297-309 ◽  
Author(s):  
A. T. Winfree
Keyword(s):  
Mathematical Models ◽  
Chemical Reactions ◽  
Heart Muscle ◽  
Local Reaction ◽  
Three Dimensional ◽  
Vortex Filament ◽  
Local Geometry ◽  
Lateral Motion ◽  
Local Activation ◽  
Vortex Lines

Three-dimensional continua capable of recurrent local activation are observed—both in the laboratory and in mathematical models—to support persistent self-organizing patterns of activity most conveniently described in terms of vortex lines. These lines generally close in rings, which may be linked and knotted. In some cases they adopt stable configurations resembling tiny dynamos of millimeter dimensions. The dynamics of these “organizing centers” has been investigated in certain chemical reactions, in heart muscle, and numerically in digital computers. The pertinent mathematical principles appear to entail consequences of local reaction and neighborhood diffusion, in the form of a dependency of the vortex filament’s lateral motion upon its local geometry and, when too closely approached by another segment of vortex filament, upon the distance and orientation involved.

scholarly journals Bounds for Euler from vorticity moments and line divergence

2013 ◽  
Vol 729 ◽  
Author(s):  
Robert M. Kerr
Keyword(s):  
Exponential Growth ◽  
Three Dimensional ◽  
Upper Bounds ◽  
Navier Stokes ◽  
Second Phase ◽  
Initial Condition ◽  
Vortex Lines ◽  
Significant Divergence ◽  
Initial Power

AbstractThe inviscid growth of a range of vorticity moments is compared using Euler calculations of anti-parallel vortices with a new initial condition. The primary goal is to understand the role of nonlinearity in the generation of a new hierarchy of rescaled vorticity moments in Navier–Stokes calculations where the rescaled moments obey ${D}_{m} \geq {D}_{m+ 1} $, the reverse of the usual ${\Omega }_{m+ 1} \geq {\Omega }_{m} $ Hölder ordering of the original moments. Two temporal phases have been identified for the Euler calculations. In the first phase the $1\lt m\lt \infty $ vorticity moments are ordered in a manner consistent with the new Navier–Stokes hierarchy and grow in a manner that skirts the lower edge of possible singular growth with ${ D}_{m}^{2} \rightarrow \sup \vert \boldsymbol{\omega} \vert \sim A_{m}{({T}_{c} - t)}^{- 1} $ where the ${A}_{m} $ are nearly independent of $m$. In the second phase, the new ${D}_{m} $ ordering breaks down as the ${\Omega }_{m} $ converge towards the same super-exponential growth for all $m$. The transition is identified using new inequalities for the upper bounds for the $- \mathrm{d} { D}_{m}^{- 2} / \mathrm{d} t$ that are based solely upon the ratios ${D}_{m+ 1} / {D}_{m} $, and the convergent super-exponential growth is shown by plotting $\log (\mathrm{d} \log {\Omega }_{m} / \mathrm{d} t)$. Three-dimensional graphics show significant divergence of the vortex lines during the second phase, which could be what inhibits the initial power-law growth.

scholarly journals Controlled creation and decay of singly-quantized vortices in a polar magnetic phase

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Y. Xiao ◽  
M. O. Borgh ◽  
L. S. Weiss ◽  
A. A. Blinova ◽  
J. Ruostekoski ◽  
...  
Keyword(s):  
High Energy Physics ◽  
Magnetic Phase ◽  
Three Dimensional ◽  
High Energy ◽  
Einstein Condensate ◽  
Quantized Vortices ◽  
Ferromagnetic Phase ◽  
Bose Einstein Condensate ◽  
Vortex Lines ◽  
Bose Einstein

AbstractQuantized vortices appear in physical systems from superfluids and superconductors to liquid crystals and high energy physics. Unlike their scalar cousins, superfluids with complex internal structure can exhibit rich dynamics of decay and even fractional vorticity. Here, we experimentally and theoretically explore the creation and time evolution of vortex lines in the polar magnetic phase of a trapped spin-1 87Rb Bose–Einstein condensate. A process of phase-imprinting a nonsingular vortex, its decay into a pair of singular spinor vortices, and a rapid exchange of magnetic phases creates a pair of three-dimensional, singular singly-quantized vortex lines with core regions that are filled with atoms in the ferromagnetic phase. Atomic interactions guide the subsequent vortex dynamics, leading to core structures that suggest the decay of the singly-quantized vortices into half-quantum vortices.

The three-dimensional structure of the wake of a circular cylinder

1966 ◽  
Vol 25 (1) ◽  
pp. 143-164 ◽  
Author(s):  
J. H. Gerrard
Keyword(s):  
Circular Cylinder ◽  
Growth And Development ◽  
Free Stream ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
The Body ◽  
Dimensional Structure ◽  
Vortex Wake ◽  
Vortex Lines ◽  
Critical Scrutiny

A critical scrutiny of the nature of the three-dimensional characteristics of the vortex wake of a circular cylinder serves to suggest lines for further investigation and furnishes some ideas on the nature of the growth and development of these non-uniformities. It is suggested that the basic occurrence in the growth of three-dimensionality is the continuation of vortex lines, oriented more or less parallel to the body, into the direction of the free stream. The causes of this vary, as do the details of the development with the particular situation considered.Experiments were performed in a wind tunnel at Reynolds numbers based on cylinder diameter of 85, 235 and 2 × 104, at which stable, transitional and turbulent vortices were investigated.

scholarly journals Half-hedgehog spin textures in sub-100 nm soft magnetic nanodots

Nanoscale ◽  
2020 ◽  
Vol 12 (36) ◽  
pp. 18646-18653 ◽  
Author(s):  
Eider Berganza ◽  
Miriam Jaafar ◽  
Jose A. Fernandez-Roldan ◽  
Maite Goiriena-Goikoetxea ◽  
Javier Pablo-Navarro ◽  
...  
Keyword(s):  
Topological Charge ◽  
Room Temperature ◽  
Three Dimensional ◽  
Soft Magnetic ◽  
Magnetic Nanodots ◽  
Chiral Structures

Permalloy hemispherical nanodots are able to host three-dimensional chiral structures (half-hedgehog spin textures) with non-zero topological charge at room temperature and in absence of DMI interaction.

Assessment of Three-Dimensional Inviscid Effects in Turbomachinery Using Simple Models

1976 ◽  
Vol 98 (2) ◽  
pp. 163-172 ◽  
Author(s):  
A. Tamura ◽  
B. Lakshminarayana
Keyword(s):  
Radial Direction ◽  
Three Dimensional ◽  
Axial Flow ◽  
Velocity Fields ◽  
Dimensional Effects ◽  
Vortex Lines ◽  
Source Line ◽  
Constant Strength ◽  
Stagger Angle ◽  
Modified Theory

The general objective of the investigation reported in this paper is to obtain a reliable understanding of the three-dimensional inviscid effects in axial flow turbomachinery. The calculation is based on the method of distributed singularities. The baldes are represented by a series of line vortices and line sources which have their axes along the radial direction and are arranged along the blade mean camber surface. The basic perturbed velocity fields due to radial vortex lines of constant strength and radial source lines of variable strength are computed from a modified theory based on Tyson’s and Rossow’s formulation. Examples illustrating the three-dimensional effects due to hub/tip ratio, stagger angle, and number of blades are carried out. The effects of the radial variation of the strength of the radial source line are examined. The three-dimensional effects are found to be appreciable for a low hub/tip configuration with small number of blades.

Coherence and Complexity in Condensed Matter: Josephson Junction Arrays

1997 ◽  
Vol 07 (05) ◽  
pp. 979-988 ◽  
Author(s):  
D. Domínguez ◽  
A. R. Bishop ◽  
N. Grønbech-Jensen
Keyword(s):  
Molecular Dynamics ◽  
Josephson Junction ◽  
Large Scale ◽  
Condensed Matter ◽  
Flux Line ◽  
Three Dimensional ◽  
Topological Excitations ◽  
Josephson Junction Arrays ◽  
Vortex Lines ◽  
Junction Arrays

The importance of the mesoscopic bridge between microscopic and mesoscopic descriptions of complex, nonlinear-nonequilibrium extended dynamical systems is illustrated in a condensed matter context through three-dimensional Josephson junction arrays. Large-scale Langevin molecular dynamics is used to study novel transformer and melting effects, emphasizing the central roles of topological excitations (flux vortex lines) in determining mesoscopic patterns and dynamics — through flux line creation, annihilation, interaction and statistical mechanics.

COMPUTER SIMULATION OF THREE-DIMENSIONAL VORTEX DYNAMICS

1986 ◽  
Vol 01 (03) ◽  
pp. 221-230 ◽  
Author(s):  
M.E. AGISHTEIN ◽  
A.A. MIGDAL
Keyword(s):  
Computer Simulation ◽  
Velocity Field ◽  
Hamiltonian System ◽  
Vortex Dynamics ◽  
Discrete Model ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Vortex Lines ◽  
Onset Of Turbulence ◽  
Generalized Hamiltonian System

The discrete model, approximating with exponential accuracy the set of interacting closed vortex lines in an ideal fluid, is proposed and investigated by means of the computer. The vortex lines move in their own velocity field according to the Biot-Savart law. This is a generalized Hamiltonian system possessing in addition an infinite number of conservation laws. Nevertheless, the motion becomes stochastic for certain initial conditions, and may be interpreted as marking the onset of turbulence.

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