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Palindromic factorization of rich words

Combinatorics 2022-04-26 v1 Discrete Mathematics

Abstract

A finite word ww is called \emph{rich} if it contains w+1\vert w\vert+1 distinct palindromic factors including the empty word. For every finite rich word ww there are distinct nonempty palindromes w1,w2,,wpw_1, w_2,\dots,w_p such that w=wpwp1w1w=w_pw_{p-1}\cdots w_1 and wiw_i is the longest palindromic suffix of wpwp1wiw_pw_{p-1}\cdots w_i, where 1ip1\leq i\leq p. This palindromic factorization is called \emph{UPS-factorization}. Let luf(w)=pluf(w)=p be \emph{the length of UPS-factorization} of ww. In 2017, it was proved that there is a constant cc such that if ww is a finite rich word and n=wn=\vert w\vert then luf(w)cnlnnluf(w)\leq c\frac{n}{\ln{n}}. We improve this result as follows: There are constants μ,π\mu, \pi such that if ww is a finite rich word and n=wn=\vert w\vert then luf(w)μneπlnn\mbox.luf(w)\leq \mu\frac{n}{e^{\pi\sqrt{\ln{n}}}}\mbox{.} The constants c,μ,πc,\mu,\pi depend on the size of the alphabet.

Keywords

Cite

@article{arxiv.2110.13078,
  title  = {Palindromic factorization of rich words},
  author = {Josef Rukavicka},
  journal= {arXiv preprint arXiv:2110.13078},
  year   = {2022}
}
R2 v1 2026-06-24T07:10:12.092Z