An analogue for semigroups of a group problem of P. Erdös and B. H. Neumann
Luise-Charlotte Kappe, John C. Lennox, James Wiegold · Bulletin of the Australian Mathematical Society · 2001
In response to a question posed by P. Erdös, B. H. Neumann showed that in a group with every subset of pairwise noncommuting elements finite there is a bound on the size of these sets. Recently, H. E. Bell, A. A. Klein and the first author showed that a similar result holds for rings. However in the case of semigroups, finiteness of subsets of pairwise noncommuting elements does not assure the existence of a bound for their size. The largest class of semigroups in which we found Neumann's result valid are cancellative semigroups.