Simulating binary trees on X-trees (extended abstract)

We show how to embed an arbitrary binary i re.e with dilation 11 and optimal expansion into an X-tree. To our knowledge this is the first result proving that every binary t rce can be si mulated by a “natural” network of bounded degree with constant dilation and constant expansion. Our construction also leads to a universal graph of bounded degree for binary trees, the degree bound being at most 415.