Maximising Bernoulli measures and dimension gaps for countable branched systems

Kifer, Peres, and Weiss proved in [A dimension gap for continued fractions with independent digits. Israel J. Math.124 (2001), 61–76] that there exists c₀ > 0, such that dim μ ≤ 1-c₀ for any probability measure μ, which makes the digits of the continued fraction expansion independent and identically distributed random variables. In this paper we prove that amongst this class of measures, there exists one whose dimension is maximal. Our results also apply in the more general setting of countable branched systems.