Extending finite subsets of an immune set
A set \(A\) is non-immune iff there exists an effective procedure that extends each finite subset of \(A\) to a strict superset that is also a finite subset of \(A\). However, an immune set can admit an effective procedure that extends its finite subsets of certain cardinalities to finite subsets of certain other cardinalities. The authors develop this idea and explore its connections with classical notions of RET theory, such as combinatorial operators and frames.
scientific article; zbMATH DE number 1051527