A Higher Bachmann-Howard Principle
Anton Freund · arXiv (Cornell University) · 2017
We present a higher well-ordering principle which is equivalent (over Simpson's set theoretic version of $\text{ATR}_0$) to the existence of transitive models of Kripke-Platek set theory, and thus to $Π^1_1$-comprehension. This is a partial solution to a conjecture of Montalbán and Rathjen: partial in the sense that our well-ordering principle is less constructive than demanded in the conjecture.