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Logic Seminar

Wednesday, October 21, 2020
12:00pm to 1:00pm
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Online Event
Borel and analytic sets in locales
Ronnie Chen, Department of Mathematics, University of Illinois at Urbana–Champaign,

A locale is, informally, a topological space without an underlying set of points, with only an abstract lattice of "open sets". Various results in the literature suggest that locale theory behaves in many ways like a generalization of descriptive set theory with countability restrictions removed. This talk will introduce locale theory from a descriptive set-theoretic point of view, and survey some known and new results which are common to both contexts. In particular, we will introduce the "∞∞-Borel hierarchy" of a locale, and sketch the existence of "σσ-analytic, non-∞∞-Borel sets".

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