Computing sets from all infinite subsets
Abstract
A set is introreducible if it can be computed by every infinite subset of itself. Such a set can be thought of as coding information very robustly. We investigate introreducible sets and related notions. Our two main results are that the collection of introreducible sets is 11-complete, so that there is no simple characterization of the introreducible sets; and that every introenumerable set has an introreducible subset.
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