The spectrum of an equational class of groupoids
Jon Froemke, Robert W. Quackenbush · Pacific Journal of Mathematics · 1975
The spectrum of an equational class % is the set of positive integers Spec(3ίΓ) = {n 1321 G JC, | 21 | = n}.It is obvious that 1 G Spec($O and JC, y G Spec(3Γ) implies xy G Spec(3O for any equational class %\ i.e.Spec(3Π is a multiplicative monoid of positive integers.Conversely, G. Gratzer showed that given any multiplicative monoid of positive integers ff there is an equational class JC such that Sf = Spec(3O.In this paper we show that j/ί can be chosen to be an equational class of groupoids.