Bqo is Pi^1_2complete
Abstract
In this paper we prove that the set of countable bqos (viewed as a subset of the Cantor space) is Pi^1_2complete. The notion of bqo or better quasiordering arises from combinatorics and is a generalization of the canonical example of a Pi^1_1complete notion, i.e. that of countable wellordering. The Pi^1_2completeness of bqo was conjectured by Clote and proved by the author in his Ph.d. thesis: in this paper we prove it using Simpson's definition of bqo and as little bqo theory as possible.
 Publication:

arXiv Mathematics eprints
 Pub Date:
 May 1994
 arXiv:
 arXiv:math/9405207
 Bibcode:
 1994math......5207M
 Keywords:

 Mathematics  Logic
 EPrint:
 Mathematical Logic Quarterly 41 (1995) 373383