|
In group theory, a dicyclic group (notation Dic''n'' or Q''4n'') is a member of a class of non-abelian groups of order 4''n'' (''n'' > 1). It is an extension of the cyclic group of order 2 by a cyclic group of order 2''n'', giving the name ''di-cyclic''. In the notation of exact sequences of groups, this extension can be expressed as: : More generally, given any finite abelian group with an order-2 element, one can define a dicyclic group. ==Definition== For each integer ''n'' > 1, the dicyclic group Dic''n'' can be defined as the subgroup of the unit quaternions generated by : More abstractly, one can define the dicyclic group Dic''n'' as any group having the presentation : Some things to note which follow from this definition: * ''x''4 = 1 * ''x''2''a''''k'' = ''a''''k''+''n'' = ''a''''k''''x''2 * if ''j'' = ±1, then ''x''''j''''a''''k'' = ''a''−''k''''x''''j''. * ''a''''k''''x''−1 = ''a''''k''−''n''''a''''n''''x''−1 = ''a''''k''−''n''''x''2''x''−1 = ''a''''k''−''n''''x''. Thus, every element of Dic''n'' can be uniquely written as ''a''''k''''x''''j'', where 0 ≤ ''k'' < 2''n'' and ''j'' = 0 or 1. The multiplication rules are given by * * * * It follows that Dic''n'' has order 4''n''.〔 When ''n'' = 2, the dicyclic group is isomorphic to the quaternion group ''Q''. More generally, when ''n'' is a power of 2, the dicyclic group is isomorphic to the generalized quaternion group.〔 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「Dicyclic group」の詳細全文を読む スポンサード リンク
|