In this paper one of our questions is the following: Which finite abelian groups are (are not) isomorphic to inner mapping groups of loops? It is well known that if the inner mapping group of a finite loop Q is abelian, then Q is centrally nilpotent. The other question is: Which properties of abelian inner mapping groups imply the central nilpotency of class at most two of the loop? After reminding the reader of the known results we show new ones. To solve these problems we transform them into group theoretical problems, then using connected transversals we get some answer.
Introduction. Q is a loop if it isa quasigroup with neutral element. The functions L a (x) = ax (left translation) and R a (x) = xa (right translation) are permutations on the elements of Q for every a ∈ Q. The permutation group generated by left and right translations M(Q) = L a , R a /a ∈ Q is called the multiplication group of Q. Denote by I (Q) the stabilizer of the neutral element in M(Q). I (Q) is a subgroup of M(Q) and it is called the inner mapping group of Q. It is clear that M(Q) is transitive and the stabilizers of the elements of Q are conjugate in M(Q). Bruck [2] introduced this connection between loops and groups, and he investigated the structure of loops by using group theory.There are several problems concerning the loops with abelian inner mapping group. One of them is the following: a) Which finite abelian groups can (cannot) occur as the inner mapping group of loops? The question which finite abelian groups are possible as inner automorphism groups of groups was completely solved by Baer [1]. The result is as follows:Let G be a finite abelian group and let G = C 1 × · · · × C n be the direct product of cyclic groups such that |C i+1 | divides |C i | (i = 1, . . . , n − 1). Then there exists a group H such that Inn(H ) ∼ = G if and only if n 2 and |C 1 | = |C 2 |.