INITIAL SEGMENTS OF THE DEGREES OF CEERS

Abstract It is known that every non-universal self-full degree in the structure of degrees computably enumerable equivalence relations (ceers) under computable reducibility has exactly one strong minimal cover. This leaves little room for embedding wide partial orders as initial segments using degrees. We show considerably more can be done by staying entirely inside collection non-self-full poset embedded an segment ceers with infinitely many classes. A further refinement proof shows also embed free distributive lattice generated lower semilattice