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On rich monoids

Radovan Gregor (1975)

Commentationes Mathematicae Universitatis Carolinae

On Rough Subgroup of a Group

Xiquan Liang, Dailu Li (2009)

Formalized Mathematics

This article describes a rough subgroup with respect to a normal subgroup of a group, and some properties of the lower and the upper approximations in a group.

On Rusakov’s n -ary r s -groups

Wiesław Aleksander Dudek, Zoran Stojaković (2001)

Czechoslovak Mathematical Journal

Properties of n -ary groups connected with the affine geometry are considered. Some conditions for an n -ary r s -group to be derived from a binary group are given. Necessary and sufficient conditions for an n -ary group < θ , b > -derived from an additive group of a field to be an r s -group are obtained. The existence of non-commutative n -ary r s -groups which are not derived from any group of arity m < n for every n 3 , r > 2 is proved.

On S -quasinormal and c -normal subgroups of a finite group

Shirong Li, Yangming Li (2008)

Czechoslovak Mathematical Journal

Let be a saturated formation containing the class of supersolvable groups and let G be a finite group. The following theorems are presented: (1) G if and only if there is a normal subgroup H such that G / H and every maximal subgroup of all Sylow subgroups of H is either c -normal or S -quasinormally embedded in G . (2) G if and only if there is a normal subgroup H such that G / H and every maximal subgroup of all Sylow subgroups of F * ( H ) , the generalized Fitting subgroup of H , is either c -normal or S -quasinormally...

On sandwich sets and congruences on regular semigroups

Mario Petrich (2006)

Czechoslovak Mathematical Journal

Let S be a regular semigroup and E ( S ) be the set of its idempotents. We call the sets S ( e , f ) f and e S ( e , f ) one-sided sandwich sets and characterize them abstractly where e , f E ( S ) . For a , a ' S such that a = a a ' a , a ' = a ' a a ' , we call S ( a ) = S ( a ' a , a a ' ) the sandwich set of a . We characterize regular semigroups S in which all S ( e , f ) (or all S ( a ) ) are right zero semigroups (respectively are trivial) in several ways including weak versions of compatibility of the natural order. For every a S , we also define E ( a ) as the set of all idempotets e such that, for any congruence ρ on...

On semiabelian groups.

Kuzennyi, N.F., Subbotin, I.Ya. (2005)

International Journal of Mathematics and Mathematical Sciences

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