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In mathematics, a solid torus is the topological space formed by sweeping a disk around a circle.〔.〕 It is homeomorphic to the Cartesian product of the disk and the circle,〔.〕 endowed with the product topology. A standard way to visualize a solid torus is as a toroid, embedded in 3-space. However, it should be distinguished from a torus, which has the same visual appearance: the torus is the two-dimensional space on the boundary of a toroid, while the solid torus includes also the interior space surrounded by the torus. ==Topological properties== The solid torus is a connected, compact, orientable 3-dimensional manifold with boundary. The boundary is homeomorphic to , the ordinary torus. Since the disk is contractible, the solid torus has the homotopy type of a circle, .〔.〕 Therefore the fundamental group and homology groups are isomorphic to those of the circle: : : 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「solid torus」の詳細全文を読む スポンサード リンク
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