
In particle theory, the skyrmion () is a hypothetical particle related originally〔At later stages the model was also related to mesons.〕 to baryons. It was described by Tony Skyrme and consists of a quantum superposition of baryons and resonance states. It could be predicted from some nuclear matter properties.〔M.R.KhoshbineKhoshnazar,"Correlated Quasiskyrmions as Alpha Particles",''Eur.Phys.J.A'' 14,207209 (2002).〕 Skyrmions as topological objects are important in solid state physics, especially in the emerging technology of spintronics. A twodimensional magnetic skyrmion, as a topological object, is formed, e.g., from a 3D effectivespin "hedgehog" (in the field of micromagnetics: out of a socalled "Bloch point" singularity of homotopy degree +1) by a stereographic projection, whereby the positive northpole spin is mapped onto a faroff edge circle of a 2Ddisk, while the negative southpole spin is mapped onto the center of the disk. ==Mathematical definition== In field theory, skyrmions are homotopically nontrivial classical solutions of a nonlinear sigma model with a nontrivial target manifold topology – hence, they are topological solitons. An example occurs in chiral models〔Chiral models stress the difference between "lefthandedness" and "righthandedness".〕 of mesons, where the target manifold is a homogeneous space of the structure group $\backslash left(\backslash frac\{SU(N)\_\backslash text\{diag\}\}\backslash cong\; SU(N)\backslash right)$ is equivalent to the ring of integers, with the congruence sign referring to homeomorphism. A topological term can be added to the chiral Lagrangian, whose integral depends only upon the homotopy class; this results in superselection sectors in the quantised model. A skyrmion can be approximated by a soliton of the SineGordon equation; after quantisation by the Bethe ansatz or otherwise, it turns into a fermion interacting according to the massive Thirring model. Skyrmions have been reported, but not conclusively proven, to be in BoseEinstein condensates, superconductors, thin magnetic films and in chiral nematic liquid crystals. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Skyrmion」の詳細全文を読む スポンサード リンク
