On restricted sumsets in abelian groups of odd order.
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.
Properties of -ary groups connected with the affine geometry are considered. Some conditions for an -ary -group to be derived from a binary group are given. Necessary and sufficient conditions for an -ary group -derived from an additive group of a field to be an -group are obtained. The existence of non-commutative -ary -groups which are not derived from any group of arity for every , is proved.
Let be a saturated formation containing the class of supersolvable groups and let be a finite group. The following theorems are presented: (1) if and only if there is a normal subgroup such that and every maximal subgroup of all Sylow subgroups of is either -normal or -quasinormally embedded in . (2) if and only if there is a normal subgroup such that and every maximal subgroup of all Sylow subgroups of , the generalized Fitting subgroup of , is either -normal or -quasinormally...
Let be a regular semigroup and be the set of its idempotents. We call the sets and one-sided sandwich sets and characterize them abstractly where . For such that , , we call the sandwich set of . We characterize regular semigroups in which all (or all are right zero semigroups (respectively are trivial) in several ways including weak versions of compatibility of the natural order. For every , we also define as the set of all idempotets such that, for any congruence on...