Variations on $\Delta^1_1$ Determinacy and $\aleph_{\omega_1}$
Abstract
We consider a seemingly weaker form of Turing determinacy. Let , is the statement: Every set of reals cofinal in the Turing degrees contains two Turing distinct, -equivalent reals. We show in : implies: for every there is a transitive model: . As a corollary: If every cofinal set of Turing degrees contains both a degree and its jump, then for every , there is a transitive model: . -- With a simple proof, this improves upon a well-known result of Harvey Friedman on the strength of Borel determinacy (though not assessed level-by-level). -- Invoking Tony Martin's proof of Borel determinacy, implies determinacy. We show further that determinacy imparts weak determinacy properties to the class .
Cite
@article{arxiv.1910.04481,
title = {Variations on $\Delta^1_1$ Determinacy and $\aleph_{\omega_1}$},
author = {Ramez L. Sami},
journal= {arXiv preprint arXiv:1910.04481},
year = {2022}
}
Comments
10 pages. Content identical to previous version: Corrected Mathjax Abstract which was a mess (author's mistake)