On Suffix Tree Breadth

The suffix tree—the compacted trie of all the suffixes of a string—is the most important and widely-used data structure in string processing. We consider a natural combinatorial question about suffix trees: for a string S of length n, how many nodes νS(d) can there be at (string) depth d in its suffix tree? We prove ν(n,d)=maxS∈ΣnνS(d) is O((n/d)logn) , and show that this bound is almost tight, describing strings for which νS(d)=d is Ω((n/d)log(n/d))