Rectangular group congruences on a semigroup
Roman S. Gigoń · Semigroup Forum · 2012
We study rectangular group congruences on an arbitrary semigroup. Some of our results are an extension of the results obtained by Masat (Proc. Am. Math. Soc. 50:107–114, 1975 ). We show that each rectangular group congruence on a semigroup S is the intersection of a group congruence and a matrix congruence and vice versa, and this expression is unique, when S is E -inversive. Finally, we prove that every rectangular group congruence on an E -inversive semigroup is uniquely determined by its kernel and trace.