Characterizing semigroups $X$ with commutative extensions $\phi (X)$, $\lambda (X)$, $N_2(X)$, $\upsilon (X)$

Abstract

We characterize semigroups $X$ whose semigroups of filters $\phi (X)$, maximal linked systems $\lambda (X)$, linked upfamilies $N_2(X)$, and upfamilies $\upsilon (X)$ are commutative.

arXiv comment16 pages