An ideal I of a ring A is essentially nilpotent if I contains a nilpotent ideal N of A such that J 91N # 0 whenever J is a nonzero ideal of A contained in I. We show that each ring A has a unique largest essentially nilpotent ideal EN(A). We study the properties of EN(A) and, in particular, we investigate how this ideal behaves with respect to related rings.

In [l] Berstein and Ganea define the nilpotence of an ü-space to be the least integer » such that the »-commutator is nullhomotopic. We prove that S3 with the usual multiplication is 4 nilpotent. Let X be an ii-space. The 2-commutator c2: XXX—>X is defined by c2(x, y) =xyx~1y~1 where the multiplication and inverses are given by the ü-space structure of X. The »-commutator cn: X"-+X is defined i...

A ring R for which x = 0 for all x e R is called a zerosquare ring. Zero-square rings are easily seen to be locally nilpotent. This leads to two problems: (1) constructing finitely generated zero-square rings with large index of nilpotence, and (2) investigating the structure of finitely generated zerosquare rings with given index of nilpotence. For the first problem we construct a class of zer...

In recent years, the RFRS condition has been used to analyze virtual fibering in 3-manifold topology. Agol’s work shows that any 3-manifold with zero Euler characteristic satisfying the RFRS condition on its fundamental group virtually fibers over the circle. In this note we will show that a finitely generated nilpotent group is either virtually abelian or is not virtually RFRS. As a corollary,...

Let t 1 be an integer and a3t(n) be the number of 3t-cores of n. We prove a class of congruences for a3t(n)mod 3 by Hecke nilpotence.