On the computational properties of the Baire Category Theorem

Sam Sanders

Published 2022-10-11Version 1

Computability theory is a discipline in the intersection of computer science and mathematical logic where the fundamental question is: given two mathematical objects X and Y, does X compute Y in principle? In case X and Y are real numbers, Turing's famous 'machine' model provides the standard interpretation of 'computation' for this question. To formalise computation involving (total) abstract objects, Kleene introduced his S1-S9 computation schemes. In turn, Dag Normann and the author have introduced a version of the lambda calculus involving fixed point operators that exactly captures S1-S9 and accommodates partial objects. In this paper, we use this new model to develop the computability theory of various well-known theorems due to Baire and Volterra and related results; these theorems only require basic mathematical notions like continuity, open sets, and density. We show that these theorems due to Baire and Volterra are computationally equivalent from the point of view of our new model, sometimes working in rather tame fragments of Goedel's T.