Algorithmic randomness, reverse mathematics, and the dominated convergence theorem
journal contributionposted on 2012-05-01, 00:00 authored by Jeremy AvigadJeremy Avigad, Edward T. Dean, Jason Rute
We analyze the pointwise convergence of a sequence of computable elements ofL1(2ω) in terms of algorithmic randomness. We consider two ways of expressing the dominated convergence theorem and show that, over the base theory RCA0, each is equivalent to the assertion that every Gδ subset of Cantor space with positive measure has an element. This last statement is, in turn, equivalent to weak weak Königʼs lemma relativized to the Turing jump of any set. It is also equivalent to the conjunction of the statement asserting the existence of a 2-random relative to any given set and the principle of Σ2 collection.