Immunity properties and the n-C.E. hierarchy

Authors:
Bahareh Afshari;George Barmpalias;S. Barry Cooper
Affiliations:
School of Mathematics, University of Leeds, Leeds, UK;School of Mathematics, University of Leeds, Leeds, UK;School of Mathematics, University of Leeds, Leeds, UK
Venue:
TAMC'06 Proceedings of the Third international conference on Theory and Applications of Models of Computation
Year:
2006

Citing 1
Cited 1

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Index sets and universal numberings

Journal of Computer and System Sciences

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Abstract

We extend Post’s programme to finite levels of the Ershov hierarchy of Δ2 sets, and characterise, in the spirit of Post [9], the degrees of the immune and hyperimmune d.c.e. sets. We also show that no properly d.c.e. set can be hh-immune, and indicate how to generalise these results to n-c.e. sets, n 2.