Spaces of functions determined by iterated limits at infinity on an oid

Abstract

In recent years many mathematicians have studied the semigroups S, the Stone-ech compactification of the discrete semigroup S, and more particularly ℕ, where ℕ is the usual semigroup of positive integers with addition (see the surveys by Hindman and Pym 6). An important role in this theory is played by sequences in S which have distinct finite sums, for these sequences are closely linked to idempotents in S (see the survey by Hindman 6). Pym 8 introduced the concept of an oid in order to show that the structure of ℕ in 5 could be obtained in a simple way for a large class of semigroups. Papazyan 7 pointed out that the theories of sequences with distinct finite sums and of oids are the same. Thus oids have a central position in the theory of semigroup compactifications.