|
In mathematics, specifically in symplectic geometry, the symplectic cut is a geometric modification on symplectic manifolds. Its effect is to decompose a given manifold into two pieces. There is an inverse operation, the symplectic sum, that glues two manifolds together into one. The symplectic cut can also be viewed as a generalization of symplectic blow up. The cut was introduced in 1995 by Eugene Lerman, who used it to study the symplectic quotient and other operations on manifolds. == Topological description == Let be any symplectic manifold and : a Hamiltonian on . Let be any regular value of , so that the level set is a smooth manifold. Assume furthermore that is fibered in circles, each of which is an integral curve of the induced Hamiltonian vector field. Under these assumptions, is a manifold with boundary , and one can form a manifold : by collapsing each circle fiber to a point. In other words, is with the subset removed and the boundary collapsed along each circle fiber. The quotient of the boundary is a submanifold of of codimension two, denoted . Similarly, one may form from a manifold , which also contains a copy of . The symplectic cut is the pair of manifolds and . Sometimes it is useful to view the two halves of the symplectic cut as being joined along their shared submanifold to produce a singular space : For example, this singular space is the central fiber in the symplectic sum regarded as a deformation. 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「Symplectic cut」の詳細全文を読む スポンサード リンク
|