scholarly journals Hyperuniformity and phase enrichment in vortex and rotor assemblies

2021 ◽  
Author(s):  
Naomi Oppenheimer ◽  
David Stein ◽  
Matan Yah Ben Zion ◽  
Michael Shelley
Keyword(s):  
Chaotic Dynamics ◽  
Hamiltonian Structure ◽  
Hexagonal Lattice ◽  
Point Vortex ◽  
Topological Defects ◽  
Natural World ◽  
Inviscid Fluid ◽  
Long Wavelength ◽  
Rotationally Invariant ◽  
Vortex Systems

Abstract Ensembles of particles rotating in a two-dimensional fluid can exhibit chaotic dynamics yet develop signatures of hidden order. Such “rotors” are found in the natural world spanning vastly disparate length scales — from the rotor proteins in cellular membranes to models of atmospheric dynamics. Here we show that an initially random distribution of either ideal vortices in an inviscid fluid, or driven rotors in a viscous membrane, spontaneously self assembles. Despite arising from drastically different physics, these systems share a Hamiltonian structure that sets geometrical conservation laws resulting in distinct structural states. We find that the rotationally invariant interactions isotropically suppress long wavelength fluctuations — a hallmark of a disordered hyperuniform material. With increasing area fraction, the system orders into a hexagonal lattice. In mixtures of two co-rotating populations, the stronger population will gain order from the other and both will become phase enriched. Finally, we show that classical 2D point vortex systems arise as exact limits of the experimentally accessible microscopic membrane rotors, yielding a new system through which to study topological defects.

scholarly journals Field-induced double spin spiral in a frustrated chiral magnet

2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Mahesh Ramakrishnan ◽  
Evan Constable ◽  
Andres Cano ◽  
Maxim Mostovoy ◽  
Jonathan S. White ◽  
...  
Keyword(s):  
Topological Defects ◽  
Electric Polarization ◽  
Fundamental Physics ◽  
Magnetic Systems ◽  
Long Wavelength ◽  
Double Spin ◽  
Potential Applications ◽  
Magnetic Skyrmions ◽  
Topological Correlations ◽  
Spin Spiral

AbstractMagnetic ground states with peculiar spin textures, such as magnetic skyrmions and multifunctional domains are of enormous interest for the fundamental physics governing their origin as well as potential applications in emerging technologies. Of particular interest are multiferroics, where sophisticated interactions between electric and magnetic phenomena can be used to tailor several functionalities. We report the direct observation of a magnetic field induced long-wavelength spin spiral modulation in the chiral compound Ba$${}_{3}$$3TaFe$${}_{3}$$3Si$${}_{2}$$2O$${}_{14}$$14, which emerges out of a helical ground state, and is hallmarked by the onset of a unique chirality-dependent contribution to the bulk electric polarization. The periodicity of the field-induced modulation, several hundreds of nm depending on the field value, is comparable to the length scales of mesoscopic topological defects such as skyrmions, merons, and solitons. The phase transition and observed threshold behavior are consistent with a phenomenology based on the allowed Lifshitz invariants for the chiral symmetry of langasite, which intriguingly contain all the essential ingredients for the realization of topologically stable antiferromagnetic skyrmions. Our findings open up new directions to explore topological correlations of antiferromagnetic spintronic systems based on non-collinear magnetic systems with additional ferroic functionalities.

Statistical Mechanical Estimate of Energy Spectrum for N-Point Vortex Systems

2007 ◽  
Vol 76 (6) ◽  
pp. 064001 ◽  
Author(s):  
Mitsusada M. Sano ◽  
Yuichi Yatsuyanagi ◽  
Takeshi Yoshida ◽  
Hiroyuki Tomita
Keyword(s):  
Energy Spectrum ◽  
Point Vortex ◽  
Statistical Mechanical ◽  
Vortex Systems

scholarly journals Relative periodic orbits in point vortex systems

Nonlinearity ◽  
2004 ◽  
Vol 17 (6) ◽  
pp. 1989-2013 ◽  
Author(s):  
F Laurent-Polz
Keyword(s):  
Periodic Orbits ◽  
Point Vortex ◽  
Vortex Systems

Dynamics of a Circular Cylinder With a Passive Degree of Freedom Interacting With an Inviscid Fluid Containing a Point Vortex

2017 ◽  
Author(s):  
Phanindra Tallapragada ◽  
Beau Pollard ◽  
Vitaliy Fedonyuk
Keyword(s):  
Circular Cylinder ◽  
Minimal Model ◽  
Degrees Of Freedom ◽  
Point Vortex ◽  
Point Vortices ◽  
Degree Of Freedom ◽  
Inviscid Fluid ◽  
Recent Past ◽  
Internal Rotor ◽  
Mechanical Feedback

In the recent past the design of many aquatic robots has been inspired by the motion of fish. Actuated internal rotors or moving masses have been frequently used either for propulsion and or the control of such robots. However the effect of internal passive degrees of freedom or passive appendages on the motion of such robots is poorly understood. In this paper we present a minimal model that demonstrates the influence of passive degrees of freedom on an aquatic robot. The model is of a circular cylinder with a passive internal rotor, immersed in an inviscid fluid interacting with point vortices. We show through numerics that the motion of the cylinder containing a passive degree of freedom is significantly different than one without. These results show that the mechanical feedback via passive degrees of freedom could be a useful way to control the motion of aquatic robots.

ZITTERBEWEGUNG IN THIN FILMS OF TOPOLOGICAL INSULATORS WITH HEXAGONAL LATTICE IRRADIATED BY TERAHERTZ PULSES

2012 ◽  
Vol 26 (17) ◽  
pp. 1250106 ◽  
Author(s):  
NATALIA N. YANYUSHKINA ◽  
ALEXANDER V. ZHUKOV ◽  
MIKHAIL B. BELONENKO ◽  
THOMAS F. GEORGE
Keyword(s):  
Thin Films ◽  
Topological Insulators ◽  
Hexagonal Lattice ◽  
Control Individual ◽  
Electron Wave ◽  
Optical Pulses ◽  
Long Wavelength ◽  
Terahertz Pulses ◽  
Long Wavelength Approximation ◽  
Wavelength Approximation

We study the Zitterbewegung effect (trembling motion) in thin films of topological insulators with a hexagonal lattice in the presence of terahertz pulse pumping. We derive the analytical expression for the current density, which describes the current induced by the motion of a wave packet of electrons. The electronic subsystem is considered in the long-wavelength approximation, and the electromagnetic field is treated classically in the approximation of a constant pumping. We reveal the possibility to control individual electron wave packets by manipulating with optical pulses.

scholarly journals Self-organized dynamics and the transition to turbulence of confined active nematics

2019 ◽  
Vol 116 (11) ◽  
pp. 4788-4797 ◽  
Author(s):  
Achini Opathalage ◽  
Michael M. Norton ◽  
Michael P. N. Juniper ◽  
Blake Langeslay ◽  
S. Ali Aghvami ◽  
...  
Keyword(s):  
Chaotic Dynamics ◽  
Topological Defects ◽  
Transition To Turbulence ◽  
Director Field ◽  
Self Organized ◽  
Nematic Director ◽  
Double Spiral ◽  
Circular Flows ◽  
Periodic Dynamics

We study how confinement transforms the chaotic dynamics of bulk microtubule-based active nematics into regular spatiotemporal patterns. For weak confinements in disks, multiple continuously nucleating and annihilating topological defects self-organize into persistent circular flows of either handedness. Increasing confinement strength leads to the emergence of distinct dynamics, in which the slow periodic nucleation of topological defects at the boundary is superimposed onto a fast procession of a pair of defects. A defect pair migrates toward the confinement core over multiple rotation cycles, while the associated nematic director field evolves from a distinct double spiral toward a nearly circularly symmetric configuration. The collapse of the defect orbits is punctuated by another boundary-localized nucleation event, that sets up long-term doubly periodic dynamics. Comparing experimental data to a theoretical model of an active nematic reveals that theory captures the fast procession of a pair of +1/2 defects, but not the slow spiral transformation nor the periodic nucleation of defect pairs. Theory also fails to predict the emergence of circular flows in the weak confinement regime. The developed confinement methods are generalized to more complex geometries, providing a robust microfluidic platform for rationally engineering 2D autonomous flows.

scholarly journals Anomalous trichromats' judgments of surface color in natural scenes under different daylights

2006 ◽  
Vol 23 (3-4) ◽  
pp. 629-635 ◽  
Author(s):  
RIGMOR C. BARAAS ◽  
DAVID H. FOSTER ◽  
KINJIRO AMANO ◽  
SÉRGIO M.C. NASCIMENTO
Keyword(s):  
High Resolution ◽  
Color Constancy ◽  
Natural World ◽  
Natural Scenes ◽  
Surface Color ◽  
Long Wavelength ◽  
Spectral Coverage ◽  
Color Monitor ◽  
Standard Color

Deuteranomalous trichromacy, which affects medium-wavelength-sensitive cones, is more common than protanomalous trichromacy, which affects long-wavelength-sensitive cones. The aim of the present work was to test the extent to which these two kinds of anomalous trichromacy affect surface-color judgments in the natural world. Simulations of 18 natural scenes under different daylight illuminants were presented on a high-resolution color monitor to 7 deuteranomalous, 7 protanomalous, and 12 normal trichromatic observers, who had to discriminate between reflectance and illuminant changes in the images. Observers' ability to judge surface color was quantified by a standard color-constancy index. Deuteranomalous trichromats performed as well as normal trichromats, but protanomalous trichromats performed more poorly than both. The results are considered in relation to the spectral coverage of cones, rod intrusion, and the characterization of anomalous trichromacy by the Rayleigh match.

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