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A very discontinuous Borel function
Published online by Cambridge University Press: 12 March 2014
Abstract
It is shown to be consistent that the reals are covered by ℵ1, meagre sets yet there is a Baire class 1 function which cannot be covered by fewer than ℵ2, continuous functions. A new cardinal invariant is introduced which corresponds to the least number of continuous functions required to cover a given function. This is characterized combinatorially. A forcing notion similar to, but not equivalent to, superperfect forcing is introduced.
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- Research Article
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- Copyright © Association for Symbolic Logic 1993
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