Soit un groupe et un sous-groupe de . Un –complément de est un sous-groupe de tel que et . Le problème auquel on s’intéresse est de classifier et décrire tous les –compléments de . Nous donnons la réponse à ce problème en trois étapes. Fixons un –complément de et soient les actions canoniques associées à la factorisation . On commence par déformer en un nouveau –complément à l’aide d’une certaine fonction appelée fonction de déformation de . Ensuite on donne la description de tous les –compléments : est un –complément de si et seulement si est isomorphe à pour une certaine fonction de déformation . Enfin, la classification des –compléments prouve qu’il existe une bijection entre les classes d’isomorphisme de tous les –compléments de et un objet cohomologique . Comme application, on démontre que la formule qui calcule le nombre de classes d’isomorphisme des groupes d’ordre peut être retrouvée à partir de la factorisation .
Let be a subgroup of a group . An –complement of is a subgroup of such that and . The classifying complements problem asks for the description and classification of all –complements of . We shall give the answer to this problem in three steps. Let be a given –complement of and the canonical left/right actions associated to the factorization . First, is deformed to a new –complement of , denoted by , using a deformation map of the matched pair . Then the description of all complements is given: is an –complement of if and only if is isomorphic to , for some deformation map . Finally, the classification of complements proves that there exists a bijection between the isomorphism classes of all –complements of and a cohomological object . As an application we show that the theoretical formula for computing the number of isomorphism types of all groups of order arises only from the factorization .
Keywords: Matched pairs, bicrossed products, the classification of finite groups
Mot clés : Paires appariées, produits (bi)croisés, classification des groupes finis.
@article{AIF_2015__65_3_1349_0, author = {Agore, Ana-Loredana and Militaru, Gigel}, title = {Classifying complements for groups. {Applications}}, journal = {Annales de l'Institut Fourier}, pages = {1349--1365}, publisher = {Association des Annales de l{\textquoteright}institut Fourier}, volume = {65}, number = {3}, year = {2015}, doi = {10.5802/aif.2958}, language = {en}, url = {http://www.numdam.org/articles/10.5802/aif.2958/} }
TY - JOUR AU - Agore, Ana-Loredana AU - Militaru, Gigel TI - Classifying complements for groups. Applications JO - Annales de l'Institut Fourier PY - 2015 SP - 1349 EP - 1365 VL - 65 IS - 3 PB - Association des Annales de l’institut Fourier UR - http://www.numdam.org/articles/10.5802/aif.2958/ DO - 10.5802/aif.2958 LA - en ID - AIF_2015__65_3_1349_0 ER -
%0 Journal Article %A Agore, Ana-Loredana %A Militaru, Gigel %T Classifying complements for groups. Applications %J Annales de l'Institut Fourier %D 2015 %P 1349-1365 %V 65 %N 3 %I Association des Annales de l’institut Fourier %U http://www.numdam.org/articles/10.5802/aif.2958/ %R 10.5802/aif.2958 %G en %F AIF_2015__65_3_1349_0
Agore, Ana-Loredana; Militaru, Gigel. Classifying complements for groups. Applications. Annales de l'Institut Fourier, Tome 65 (2015) no. 3, pp. 1349-1365. doi : 10.5802/aif.2958. http://www.numdam.org/articles/10.5802/aif.2958/
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