Matthew Frank - Interpolating Between Choices for the Approximate Intermediate Value Theorem

lmcs:2638 - Logical Methods in Computer Science, July 14, 2020, Volume 16, Issue 3 - https://doi.org/10.23638/LMCS-16(3:5)2020
Interpolating Between Choices for the Approximate Intermediate Value TheoremArticle

Authors: Matthew Frank

    This paper proves the approximate intermediate value theorem, constructively and from notably weak hypotheses: from pointwise rather than uniform continuity, without assuming that reals are presented with rational approximants, and without using countable choice. The theorem is that if a pointwise continuous function has both a negative and a positive value, then it has values arbitrarily close to 0. The proof builds on the usual classical proof by bisection, which repeatedly selects the left or right half of an interval; the algorithm here selects an interval of half the size in a continuous way, interpolating between those two possibilities.


    Volume: Volume 16, Issue 3
    Published on: July 14, 2020
    Accepted on: June 4, 2018
    Submitted on: January 10, 2017
    Keywords: Mathematics - Logic,Computer Science - Logic in Computer Science,03F60, 03D78, 03E25, 26A15, 26E40,G.1.5

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