We exhibit several finite groups that are not active sums of cyclic subgroups. We show that this is the case for groups with $H_{1}G$ of odd order and $H_{2}G$ of even order. As particular examples of this we have the alternating groups $A_n$ for $n\geq 4$, some special and some projective linear groups. Our next set of examples consists of $p$-groups where the normalizer and the centralizer of every element coincide. We also have an example of a 2-group where the above conditions are not satisfied; thus we had to devise an ad hoc argument. We observe that the examples of $p$-groups given also provide groups that are not molecular.
Publié le : 2006-06-14
Classification:  20J05,  20D99,  20D30
@article{1152203946,
     author = {D\'\i az-Barriga, Alejandro J. and Gonz\'alez-Acu\~na, Francisco and Marmolejo, Francisco and Rom\'an, Leopoldo},
     title = {Active sums II},
     journal = {Osaka J. Math.},
     volume = {43},
     number = {2},
     year = {2006},
     pages = { 371-399},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1152203946}
}
Díaz-Barriga, Alejandro J.; González-Acuña, Francisco; Marmolejo, Francisco; Román, Leopoldo. Active sums II. Osaka J. Math., Tome 43 (2006) no. 2, pp.  371-399. http://gdmltest.u-ga.fr/item/1152203946/