Finding paths through narrow and wide trees

Abstract

We consider two axioms of second-order arithmetic. These axioms assert, in two different ways, that infinite but narrow binary trees always have infinite paths. We show that both axioms are strictly weaker than Weak König's Lemma, and incomparable in strength to the dual statement (WWKL) that wide binary trees have paths.

Contains an indication of an error in the published version, found by Laurent Bienvenu and Paul Shafer in 2012