In mathematics, in the field of group theory, a subgroup H of a group G is termed malnormal if for any x in G but not in H , H and x H x − 1 intersect in the identity element.
Some facts about malnormality:
An intersection of malnormal subgroups is malnormal.Malnormality is transitive, that is, a malnormal subgroup of a malnormal subgroup is malnormal.The trivial subgroup and the whole group are malnormal subgroups. A normal subgroup that is also malnormal must be one of these.Every malnormal subgroup is a special type of C-group called a trivial intersection subgroup or TI subgroup.When G is finite, a malnormal subgroup H distinct from 1 and G is called a "Frobenius complement". The set N of elements of G which are, either equal to 1, or non-conjugate to any element of H, is a normal subgroup of G, called the "Frobenius kernel", and G is the semi-direct product of H and N (Frobenius' theorem).
