A hierarchical version of the de Finetti and Aldous-Hoover representations
Tim Austin, Dmitry Panchenko · arXiv (Cornell University) · 2013
We consider random arrays indexed by the leaves of an infinitary rooted tree of finite depth, with the distribution invariant under the rearrangements that preserve the tree structure. We call such arrays hierarchically exchangeable and prove that they satisfy an analogue of de Finetti's theorem. We also prove a more general result for arrays indexed by several trees, which includes a hierarchical version of the Aldous-Hoover representation.