An Improper Arithmetically Closed Borel Subalgebra of P(ω) mod FIN
نویسندگان
چکیده
We show the existence of a subalgebra A ⊆ P(ω) that satisfies the following three conditions: • A is Borel (when P(ω) is identified with 2). • A is arithmetically closed (i.e., A is closed under the Turing jump, and Turing reducibility). • The forcing notion (A,⊆) modulo the ideal FIN of finite sets collapses the continuum to א0.
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