Abstract
Using the method of forcing of set theory, we prove the following two theorems on the existence of measurable choice functions: LetT be the closed unit interval [0,1] and letm be the usual Lebesgue measure defined on the Borel subsets ofT. Theorem1. LetS⊂T×T be a Borel set such that for alltεT,S t def={x|(t,x)εS} is countable and non-empty. Then there exists a countable series of Lebesgue-measurable functionsf n: T→T such thatS t={fn(t)|nεω} for alltε[0,1],W x={y|(x,y)εW} is uncountable. Then there exists a functionh:[0,1]×[0,1]→W with the following properties: (a) for each xε[0,1], the functionh(x,·) is one-one and ontoW x and is Borel measurable; (b) for eachy, h(·, y) is Lebesgue measurable; (c) the functionh is Lebesgue measurable.
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Wesley, E. Extensions of the measurable choice theorem by means of forcing. Israel J. Math. 14, 104–114 (1973). https://doi.org/10.1007/BF02761539
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DOI: https://doi.org/10.1007/BF02761539