VARIATIONS ON DETERMINACY AND

نویسندگان

چکیده

We consider a seemingly weaker form of $\Delta^1_1$ Turing determinacy. Let $2 \leq \rho < \omega_1^{\textrm{CK}}$, $\textrm{Weak-Turing-Det}_\rho (\Delta^1_1)$ is the statement: Every set reals cofinal in degrees contains two distinct, $\Delta^0_\rho$-equivalent reals. show $\textrm{ZF}^-$: implies: for every $\nu \omega_1^{\textrm{CK}}$ there transitive model: $M \models \textrm{ZF}^- + \aleph_\nu \textrm{ exists}$. As corollary: If both degree and its jump, then -- With simple proof, this improves upon well-known result Harvey Friedman on strength Borel determinacy (though not assessed level-by-level). Invoking Tony Martin's proof determinacy, implies further that imparts weak properties to class $\Sigma^1_1$.

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ژورنال

عنوان ژورنال: Journal of Symbolic Logic

سال: 2021

ISSN: ['1943-5886', '0022-4812']

DOI: https://doi.org/10.1017/jsl.2020.47