Convexities of partial monounary algebras (Q1047081)

A class of partial monounary algebras is said to be a convexity if it is closed under homomorphic images, direct products and convex relative subalgebras, the last notion having been examined by the author in an earlier paper [Czech. Math. J. 38(113), No.~4, 655--672 (1988; Zbl 0677.08004)]. It is shown that there are exactly 23 such convexities, forming a lattice under inclusion, and that each one of them can be generated by no more than two of its members.