Notes on degrees of relative computable categoricity

Abstract

We are studying the degrees in which a computable structure is relatively computably categoricity, i.e., computably categorcial among all non-computable copies of the structure. Unlike the degrees of computable categoricity we can bound the possible degrees of relative computable categoricity by the oracle 0". In the case of rigid structures the bound is in fact 0'. These estimations are precise, in particular we can build a computable structure which is relatively computably categorical only in the degrees above 0".