Splitting and non-splitting in the difference hierarchy

摘要

In this paper, we investigate splitting and non-splitting properties in the Ershov differencernhierarchy, in which area major contributions have been made by Barry Cooper with hisrnstudents and colleagues. In the first part of the paper, we give a brief survey of his researchrnin this area and discuss a number of related open questions. In the second part of the paper,rnwe consider a splitting of 0' with some additional properties.