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In mathematics, specifically in group theory, residue-class-wise affine groups are certain permutation groups acting on (the integers), whose elements are bijective residue-class-wise affine mappings. A mapping is called residue-class-wise affine if there is a nonzero integer such that the restrictions of to the residue classes (mod ) are all affine. This means that for any residue class there are coefficients such that the restriction of the mapping to the set is given by : or on subsets thereof. A particularly basic type of residue-class-wise affine permutations are the class transpositions: given disjoint residue classes and , the corresponding class transposition is the permutation of which interchanges and for every and which fixes everything else. Here it is assumed that and that . The set of all class transpositions of generates a countable simple group which has the following properties: * It is not finitely generated. * Every finite group, every free product of finite groups and every free group of finite rank embeds into it. * The class of its subgroups is closed under taking direct products, under taking wreath products with finite groups, and under taking restricted wreath products with the infinite cyclic group. * It has finitely generated subgroups which do not have finite presentations. * It has finitely generated subgroups with algorithmically unsolvable membership problem. * It has an uncountable series of simple subgroups which is parametrized by the sets of odd primes. It is straightforward to generalize the notion of a residue-class-wise affine group to groups acting on suitable rings other than , though only little work in this direction has been done so far. See also the Collatz conjecture, which is an assertion about a surjective, but not injective residue-class-wise affine mapping. == References and external links == *Stefan Kohl. Restklassenweise affine Gruppen. Dissertation, Universität Stuttgart, 2005. (Archivserver der Deutschen Nationalbibliothek ) (OPUS-Datenbank(Universität Stuttgart) ) *Stefan Kohl. (RCWA ) – Residue-Class-Wise Affine Groups. (GAP ) package. 2005. *Stefan Kohl. A Simple Group Generated by Involutions Interchanging Residue Classes of the Integers. Math. Z. 264 (2010), no. 4, 927–938. () 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「Residue-class-wise affine group」の詳細全文を読む スポンサード リンク
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