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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.Khoshbin-e-Khoshnazar,"Correlated Quasiskyrmions as Alpha Particles",''Eur.Phys.J.A'' 14,207-209 (2002).〕 Skyrmions as topological objects are important in solid state physics, especially in the emerging technology of spintronics. A two-dimensional magnetic skyrmion, as a topological object, is formed, e.g., from a 3D effective-spin "hedgehog" (in the field of micromagnetics: out of a so-called "Bloch point" singularity of homotopy degree +1) by a stereographic projection, whereby the positive north-pole spin is mapped onto a far-off edge circle of a 2D-disk, while the negative south-pole spin is mapped onto the center of the disk. ==Mathematical definition== In field theory, skyrmions are homotopically non-trivial classical solutions of a nonlinear sigma model with a non-trivial target manifold topology – hence, they are topological solitons. An example occurs in chiral models〔Chiral models stress the difference between "left-handedness" and "right-handedness".〕 of mesons, where the target manifold is a homogeneous space of the structure group 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 Sine-Gordon 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 Bose-Einstein 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
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