Parking on the infinite binary tree

Abstract

Let $$(A_u : u \in \mathbb {B})$$ be i.i.d. non-negative integers that we interpret as car arrivals on the vertices of the full binary tree $$ \mathbb {B}$$ . Each car tries to park on its arrival node, but if it is already occupied, it drives towards the root and parks on the first available spot. It is known (Bahl et al. in Parking on supercritical Galton–Watson trees, arXiv:1912.13062 , 2019; Goldschmidt and Przykucki in Comb Probab Comput 28:23–45, 2019) that the parking process on $$ \mathbb {B}$$ exhibits a phase transition in the sense that either a finite number of cars do not manage to park in expectation (subcritical regime) or all vertices of the tree contain a car and infinitely many cars do not manage to park (supercritical regime). We characterize those regimes in terms of the law of A in an explicit way. We also study in detail the critical regime as well as the phase transition which turns out to be “discontinuous”.