scholarly journals Bianchi IX cosmologies in the Einstein-Skyrme system in a sector with nontrivial topological charge

2019 ◽  
Vol 99 (4) ◽  
Author(s):  
Fabrizio Canfora ◽  
Nikolaos Dimakis ◽  
Alex Giacomini ◽  
Andronikos Paliathanasis
Keyword(s):  
Topological Charge ◽  
Bianchi Ix

scholarly journals Visualizing the strongly reshaped skyrmion Hall effect in multilayer wire devices

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Anthony K. C. Tan ◽  
Pin Ho ◽  
James Lourembam ◽  
Lisen Huang ◽  
Hang Khume Tan ◽  
...  
Keyword(s):  
Hall Effect ◽  
Topological Charge ◽  
Size Dependence ◽  
Particle Model ◽  
Model Simulations ◽  
Generation Computing ◽  
Magnetic Skyrmions ◽  
Transverse Deflection ◽  
Robust Framework ◽  
Geometric Effects

AbstractMagnetic skyrmions are nanoscale spin textures touted as next-generation computing elements. When subjected to lateral currents, skyrmions move at considerable speeds. Their topological charge results in an additional transverse deflection known as the skyrmion Hall effect (SkHE). While promising, their dynamic phenomenology with current, skyrmion size, geometric effects and disorder remain to be established. Here we report on the ensemble dynamics of individual skyrmions forming dense arrays in Pt/Co/MgO wires by examining over 20,000 instances of motion across currents and fields. The skyrmion speed reaches 24 m/s in the plastic flow regime and is surprisingly robust to positional and size variations. Meanwhile, the SkHE saturates at ∼22∘, is substantially reshaped by the wire edge, and crucially increases weakly with skyrmion size. Particle model simulations suggest that the SkHE size dependence — contrary to analytical predictions — arises from the interplay of intrinsic and pinning-driven effects. These results establish a robust framework to harness SkHE and achieve high-throughput skyrmion motion in wire devices.

scholarly journals Effect of Deformation on Topological Properties of Cobalt Monosilicide

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 143
Author(s):  
Sergey Nikolaev ◽  
Dmitry Pshenay-Severin ◽  
Yuri Ivanov ◽  
Alexander Burkov
Keyword(s):  
Band Structure ◽  
Ab Initio Calculations ◽  
Topological Charge ◽  
External Stress ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Topological Properties ◽  
Uniaxial Deformation ◽  
Band Crossing ◽  
Topological Charges

Recently, it was shown that materials with certain crystal structures can exhibit multifold band crossings with large topological charges. CoSi is one such material that belongs to non-centrosymmetric space group P213 (#198) and posseses multifold band crossing points with a topological charge of 4. The change of crystal symmetry, e.g., by means of external stress, can lift the degeneracy and change its topological properties. In the present work, the influence of uniaxial deformation on the band structure and topological properties of CoSi is investigated on the base of ab initio calculations. The k·p Hamiltonian taking into account deformation is constructed on the base of symmetry consideration near the Γ and R points both with and without spin-orbit coupling. The transformation of multifold band crossings into nodes of other types with different topological charges, their shift both in energy and in reciprocal space and the tilt of dispersion around nodes are studied in detail depending on the direction of uniaxial deformation.

scholarly journals Electroweak axion string and superconductivity

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Yoshihiko Abe ◽  
Yu Hamada ◽  
Koichi Yoshioka
Keyword(s):  
Electric Current ◽  
Early Universe ◽  
Parameter Space ◽  
Cosmic String ◽  
Topological Charge ◽  
Attractive Force ◽  
Electroweak Scale ◽  
Large Current

Abstract We study the axion strings with the electroweak gauge flux in the DFSZ axion model and show that these strings, called the electroweak axion strings, can exhibit superconductivity without fermionic zeromodes. We construct three types of electroweak axion string solutions. Among them, the string with W-flux can be lightest in some parameter space, which leads to a stable superconducting cosmic string. We also show that a large electric current can flow along the string due to the Peccei-Quinn scale much higher than the electroweak scale. This large current induces a net attractive force between the axion strings with the same topological charge, which opens a novel possibility that the axion strings form Y-junctions in the early universe.

scholarly journals High-Efficiency Spin-Related Vortex Metalenses

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1485
Author(s):  
Wei Wang ◽  
Ruikang Zhao ◽  
Shilong Chang ◽  
Jing Li ◽  
Yan Shi ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Topological Charge ◽  
High Efficiency ◽  
Infrared Band ◽  
Mid Infrared ◽  
Integrated Devices ◽  
Vortex Beams ◽  
Topological Charges

In this paper, one spin-selected vortex metalens composed of silicon nanobricks is designed and numerically investigated at the mid-infrared band, which can produce vortex beams with different topological charges and achieve different spin lights simultaneously. Another type of spin-independent vortex metalens is also designed, which can focus the vortex beams with the same topological charge at the same position for different spin lights, respectively. Both of the two vortex metalenses can achieve high-efficiency focusing for different spin lights. In addition, the spin-to-orbital angular momentum conversion through the vortex metalens is also discussed in detail. Our work facilitates the establishment of high-efficiency spin-related integrated devices, which is significant for the development of vortex optics and spin optics.

scholarly journals Supercontinuum optical vortex pulse generation without spatial or topological-charge dispersion

2009 ◽  
Vol 17 (17) ◽  
pp. 14517 ◽  
Author(s):  
Yu Tokizane ◽  
Kazuhiko Oka ◽  
Ryuji Morita
Keyword(s):  
Topological Charge ◽  
Optical Vortex ◽  
Pulse Generation

scholarly journals Mie scattering distinguishes the topological charge of an optical vortex: a homage to Gustav Mie

2009 ◽  
Vol 11 (1) ◽  
pp. 013046 ◽  
Author(s):  
Valeria Garbin ◽  
Giovanni Volpe ◽  
Enrico Ferrari ◽  
Michel Versluis ◽  
Dan Cojoc ◽  
...  
Keyword(s):  
Topological Charge ◽  
Optical Vortex ◽  
Mie Scattering

A COMMENT ON TOPOLOGICAL FIELD THEORY QUANTIZATION AND STOCHASTIC PROCESSES

1990 ◽  
Vol 05 (19) ◽  
pp. 3777-3786 ◽  
Author(s):  
L.F. CUGLIANDOLO ◽  
G. LOZANO ◽  
H. MONTANI ◽  
F.A. SCHAPOSNIK
Keyword(s):  
Field Theory ◽  
Equilibrium State ◽  
Stochastic Processes ◽  
Topological Field Theories ◽  
Topological Charge ◽  
Field Theories ◽  
Langevin Equations ◽  
Topological Field Theory ◽  
Topological Field

We discuss the relation between different quantization approaches to topological field theories by deriving a connection between Bogomol’nyi and Langevin equations for stochastic processes which evolve towards an equilibrium state governed by the topological charge.

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