Random trees constructed by aggregation

We study a general procedure that builds random R -trees by gluing recursively a new branch on a uniform point of the pre-existing tree. The aim of this paper is to see how the asymptotic behavior of the sequence of lengths of branches influences some geometric pr operties of the limiting tree, such as compactness and Hausdorff dimension. In particular, when the seq uence of lengths of branches behaves roughly like n − α for some α ∈ (0 , 1], we show that the limiting tree is a compact random tree of Hausdor ff dimension α − 1 . This encompasses the famous construction of the Brownian tree of Aldous. When α > 1, the limiting tree is thinner and its Hausdorff dimension is always 1. In tha t case, we show that α − 1 corresponds to the dimension of the set of leaves of the tree.no