  We consider the problem whether for a group G there exists a constant
Lambda(G) > 1 such that for any (r,s)-matrix A over the integral group ring ZG
the Fuglede-Kadison determinant of the G-equivariant bounded operator from
L^2(G)^r to L^2(G)^s given by right multiplication with A is either one or
greater or equal to Lambda(G). If G is the infinite cyclic group and we
consider only r = s = 1, this is precisely Lehmer's problem.
