Multisoliton configurations in Skyrme-like models

2007 ◽  
Vol 85 (6) ◽  
pp. 679-685 ◽  
Author(s):  
J -P Longpré ◽  
L Marleau

We explore the higher topological charge sector for generalized SU(2) Skyrme models in search of the static-field configuration with the lowest energy that would better reproduce what is expected for nuclei. Indeed the Skyrme model leads, for example, to toroidal, tetrahedral, and cubic symmetries for B = 2, 3, and 4 configurations, respectively, whereas nucleons in nuclei are presumably preserving their individuality. It turns out that the symmetries of the soliton solutions for the extended Skyrme models presented in this work are the same as for the Skyrme model at least for topological charges B < 5, which suggest that the Skyrme model has to be modified significantly to preserve the individual nature of the nucleons in nuclei. PACS Nos.: 12.39.Dc, 10.11.Lm


Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 143
Author(s):  
Sergey Nikolaev ◽  
Dmitry Pshenay-Severin ◽  
Yuri Ivanov ◽  
Alexander Burkov

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.



Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1485
Author(s):  
Wei Wang ◽  
Ruikang Zhao ◽  
Shilong Chang ◽  
Jing Li ◽  
Yan Shi ◽  
...  

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.



2021 ◽  
Author(s):  
Cheng Cui ◽  
Zheng Liu ◽  
Bin Hu ◽  
Yurong Jiang ◽  
Juan Liu

Abstract Tunable metasurface devices are considered to be an important link for metasurfaces to practical applications due to their functional diversity and high adaptability to the application scenarios. Metasurfaces have unique value in the generation of vortex beams because they can realize light wavefronts of any shape. In recent years, several vortex beam generators using metasurfaces have been proposed. However, the topological charge generally lacks tunability, which reduces the scope of their applications. Here, we propose an active tunable multi-channeled vortex beam switch based on a moiré structure composed of two cascaded dielectric metasurfaces. The simulation results show that when linearly polarized light with a wavelength of 810 nm is incident, the topological charge from -6 to +6 can be continuously generated by relatively rotating the two metasurfaces. Meanwhile, different topological charges are deflected to different spatial channels, realizing the function of multi-channeled signal transmission. We also study the efficiency and broadband performance of the structure. The proposed multi-channeled separation method of vortex beams that can actively tune topological charges paves the way for the compactness and functional diversity of devices in the fields of optical communications, biomedicine, and optoelectronics.



Author(s):  
Nick Allcock ◽  
Ruth Day

This chapter aims to provide you with the knowledge to be able to take an evidence-based approach to the nursing management of people who are experiencing pain. As a practising nurse, pain will be something that many of your patients will experience; however, one individual’s pain may be very different from another person’s. Pain can vary depending on the circumstances in which it is experienced and the individual characteristics of the person experiencing it. Understanding someone’s pain experience is therefore challenging because you cannot see someone’s pain or easily judge how bad it is, what it feels like, or how it affects him or her. This chapter provides you with knowledge and skills to recognize, assess, and manage the patient’s experience of pain effectively with evidence-based strategies. The variability of the experience of pain makes defining pain difficult. Pain is something that we have all experienced at some point in our lives and therefore, through these experiences, we have developed an understanding of what we consider to be pain. One of the most widely accepted definitions is that of the International Association for the Study of Pain (IASP), which defines pain as:…An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. (Merskey and Bogduk,1994)…Although this definition is often quoted, the difficulty in defining pain is illustrated by the fact that the IASP added a note (go to http://www.iasp-pain.org/ and search for ‘pain definitions’) to highlight the individual nature of pain and the fact that pain is a sensory experience with an emotional component. The individual nature of pain is also highlighted by another commonly used definition:…Pain is whatever the experiencing person says it is and happens whenever he/she says it does. (McCaffery, 1972)…This definition highlights the fact that pain is an individual experience and that measuring pain objectively is difficult. Therefore asking the person and actively listening to the self-report of the experience is the best way in which to understand another person’s pain. A common criticism of McCaffery’s definition is that some people cannot say what they are experiencing.



2019 ◽  
Vol 34 (34) ◽  
pp. 1950284
Author(s):  
Ernesto A. Matute

The Standard Model (SM) with one right-handed neutrino per generation is revisited with presymmetry being the global [Formula: see text] symmetry of an electroweak theory of leptons and quarks with initially postulated symmetric fractional charges. The cancellation of gauge anomalies and the non-perturbative normalization of lepton charges proceed through the mixing of local and topological charges, the global [Formula: see text] measuring the induced charge associated with a unit of topological charge, and the mathematical replacement of the original fractional charges with the experimentally observed ones. The [Formula: see text] symmetry of the SM with Dirac neutrinos is seen as a residual presymmetry. High-scale and low-scale seesaw mechanisms proposed to explain the mass of neutrinos are examined from the perspective of presymmetry, be they of Majorana or pseudo-Dirac type. We find that the tiny mass splitting in pseudo-Dirac neutrinos and the mass of heavy neutrinos ride on the opposite ends of the seesaw. We show that pseudo-Dirac neutrinos contain extra sterile neutrinos with imprints of presymmetry and for heavy ones we get constraints favoring the low-scale linear seesaw over the inverse variant.



2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Sven Bjarke Gudnason ◽  
Marco Barsanti ◽  
Stefano Bolognesi

Abstract We consider the baby-Skyrme model in the regime close to the so-called restricted baby-Skyrme model, which is a BPS model with area-preserving diffeomorphism invariance. The perturbation takes the form of the standard kinetic Dirichlet term with a small coefficient ϵ. Classical solutions of this model, to leading order in ϵ, are called restricted harmonic maps. In the BPS limit (ϵ → 0) of the model with the potential being the standard pion-mass term, the solution with unit topological charge is a compacton. Using analytical and numerical arguments we obtain solutions to the problem for topological sectors greater than one. We develop a perturbative scheme in ϵ with which we can calculate the corrections to the BPS mass. The leading order ($$ \mathcal{O}\left({\upepsilon}^1\right) $$ O ϵ 1 ) corrections show that the baby Skyrmion with topological charge two is energetically preferred. The binding energy requires us to go to the third order in ϵ to capture the relevant terms in perturbation theory, however, the binding energy contributes to the total energy at order ϵ2. We find that the baby Skyrmions — in the near-BPS regime — are compactons of topological charge two, that touch each other on their periphery at a single point and with orientations in the attractive channel.



1993 ◽  
Vol 08 (34) ◽  
pp. 3241-3250 ◽  
Author(s):  
L. MARTINA ◽  
O.K. PASHAEV ◽  
G. SOLIANI

A self-dual Chern-Simons system and its Lax pair are derived from the tangent space representation of a two-dimensional nonlinear σ-model, endowed with a gauge field. The related “matter” field density obeys the Liouville equation, whose N-soliton solutions correspond to the magnetic vortices in the static self-dual planar Heisenberg model. It is shown that the topological charge and the total vorticity correspond to the electric charge and the magnetic flux for the Chern-Simons system, respectively. General holomorphic solutions of the system studied generate a large class of static solutions to the Davey-Stewartson and Ishimori equations.



1995 ◽  
Vol 10 (13) ◽  
pp. 1879-1903 ◽  
Author(s):  
ULI HARDER ◽  
ALEXANDER A. ISKANDAR ◽  
WILLIAM A. McGHEE

Explicit constructions [Formula: see text] of affine Toda field theory breather solutions are presented. Breathers arise either from two solitons of the same species or from solitons which are antispecies of each other. In the first case, breathers carry topological charges. These topological charges lie in the tensor product representation of the fundamental representations associated with the topological charges of the constituent solitons. In the second case, breathers have zero topological charge. The breather masses are, as expected, less than the sum of the masses of the constituent solitons.



2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Tony Gherghetta ◽  
Alex Pomarol

Abstract Small instantons can play an important role in Yang-Mills theories whose gauge couplings are sizeable at small distances. An interesting class of theories where this could occur is in weakly-gauged holographic models (dual to Yang-Mills theories interacting with strongly-coupled CFTs), since gauge couplings are indeed enhanced towards the UV boundary of the 5D AdS space. However, contrary to expectations, we show that small instantons in these non-asymptotically-free models are highly suppressed and ineffective. This is due to the conservation of topological charge that forbids instantons to be localized near the UV boundary. Despite this fact we find non-trivial UV localized instanton-anti-instanton solutions of the Yang-Mills equations where the topological charges annihilate in the AdS bulk. These analytic solutions arise from a 5D conformal transformation of the uplifted 4D instanton. Our analysis therefore reveals unexpected nonperturbative configurations of Yang-Mills theories when they interact with strongly-coupled CFTs.



2020 ◽  
Vol 44 (6) ◽  
pp. 901-908
Author(s):  
V.V. Kotlyar ◽  
A.A. Kovalev ◽  
E.S. Kozlova ◽  
A.P. Porfirev

We investigate a multispiral phase plate (MSPP) with multiple centers of phase singularity arbitrarily located in the MSPP plane. Equations to describe the topological charge of an optical vortex in the initial plane immediately behind the MSPP and orbital angular momentum (OAM) normalized relative to the beam power are derived. The topological charge in the initial plane is found as a sum of the topological charges of all singularities if their centers are located inside a finite-radius circular aperture. If the phase singularity centers are partially located on the boundary of a circular diaphragm limiting the MSPP, the total topological charge is found as the sum of all singularities divided by 2. Total OAM that the vortex carries depends on the location of the singularity centers: the farther from the center of the plate the singularity center is located, the smaller is its contribution to the OAM. If all singularity centers are located on the boundary of the diaphragm limiting MSPP, then the OAM of the vortex beam equals zero, although in this case the topological charge of the beam is nonzero.



Sign in / Sign up

Export Citation Format

Share Document