A4 Refereed article in a conference publication

On k-abelian palindromic rich and poor words




AuthorsKarhumäki J., Puzynina S.

EditorsArseny M. Shur, Mikhail V. Volkov

Conference nameDevelopments in Language Theory

PublisherSpringer Verlag

Publication year2014

Book title Developments in Language Theory

Journal name in sourceLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Series titleLecture Notes in Computer Science

Number in series8633

First page 191

Last page202

ISBN978-3-319-09697-1

eISBN978-3-319-09698-8

ISSN0302-9743

DOIhttps://doi.org/10.1007/978-3-319-09698-8_17

Web address http://api.elsevier.com/content/abstract/scopus_id:84906495395


Abstract

A word is called a palindrome if it is equal to its reversal. In the paper we consider a k-abelian modification of this notion. Two words are called k-abelian equivalent if they contain the same number of occurrences of each factor of length at most k. We say that a word is a k-abelian palindrome if it is k-abelian equivalent to its reversal. A question we deal with is the following: how many distinct palindromes can a word contain? It is well known that a word of length n can contain at most n+1 distinct palindromes as its factors; such words are called rich. On the other hand, there exist infinite words containing only finitely many distinct palindromes as their factors; such words are called poor. It is easy to see that there are no abelian poor words, and there exist words containing Θ(n ) distinct abelian palindromes. We analyze these notions with respect to k-abelian equivalence. We show that in the k-abelian case there exist poor words containing finitely many distinct k-abelian palindromic factors, and there exist rich words containing Θ(n ) distinct k-abelian palindromes as their factors. Therefore, for poor words the situation resembles normal words, while for rich words it is similar to the abelian case. © 2014 Springer International Publishing Switzerland.




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