A logical analysis of the generalized Banach contractions principle

Alexander Kreuzer
2012 Journal of Logic and Analysis  
The generalized Banach contractions principle states that each g-contraction has a fixed point. We show that this principle is a consequence of Ramsey's theorem for pairs over, roughly, RCA 0 + Σ 0 2 -IA.
doi:10.4115/jla.2012.4.17 fatcat:rl4gnjb7fjg5jd6uj66oc72i4y