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I'm looking for a measure-theoretic analogue to the disjoint union topology, or for work on the $\sigma$-algebra generated by canonical injections. More formally: For an indexed family of sets $\{A_i\...

Currently I am reading some basic literature on descriptive set theory and boolean algebras. And this comes out a lot, for example in results like: Let $X$ and $Y$ be topological spaces, and $f:X \to ...