English

A Higher Bachmann-Howard Principle

Logic 2018-09-20 v2

Abstract

We present a higher well-ordering principle which is equivalent (over Simpson's set theoretic version of ATR0\text{ATR}_0) to the existence of transitive models of Kripke-Platek set theory, and thus to Π11\Pi^1_1-comprehension. This is a partial solution to a conjecture of Montalb\'an and Rathjen: partial in the sense that our well-ordering principle is less constructive than demanded in the conjecture.

Keywords

Cite

@article{arxiv.1704.01662,
  title  = {A Higher Bachmann-Howard Principle},
  author = {Anton Freund},
  journal= {arXiv preprint arXiv:1704.01662},
  year   = {2018}
}

Comments

This paper is no longer up to date: It is superseded by the author's PhD thesis (available at http://etheses.whiterose.ac.uk/20929/) and the streamlined presentation in arXiv:1809.06759. In contrast to the present abstract, we have now found a computable version of our well-ordering principle. Thus the conjecture by Montalb\'an and Rathjen can be considered as fully solved

R2 v1 2026-06-22T19:09:14.317Z