New approach to nonrepetitive sequences

2013
journal article
article
cris.lastimport.scopus2024-04-26T01:18:50Z
dc.abstract.enA sequence is nonrepetitive if it does not contain two adjacent identical blocks. The remarkable construction of Thue asserts that three symbols are enough to build an arbitrarily long nonrepetitive sequence. It is still not settled whether the following extension holds: for every sequence of three-element sets L1,…,Ln there exists a nonrepetitive sequence s1,…,sn with si∈Li. We propose a new non-constructive way to build long nonrepetitive sequences and provide an elementary proof that sets of size 4 suffice confirming the best known bound. The simple double counting in the heart of the argument is inspired by the recent algorithmic proof of the Lovász local lemma due to Moser and Tardos. Furthermore we apply this approach and present game-theoretic type results on nonrepetitive sequences. Nonrepetitive game is played by two players who pick, one by one, consecutive terms of a sequence over a given set of symbols. The first player tries to avoid repetitions, while the second player, in contrast, wants to create them. Of course, by simple imitation, the second player can force lots of repetitions of size 1. However, as proved by Pegden, there is a strategy for the first player to build an arbitrarily long sequence over 37 symbols with no repetitions of size greater than 1. Our techniques allow to reduce 37–6. Another game we consider is the erase-repetition game. Here, whenever a repetition occurs, the repeated block is immediately erased and the next player to move continues the play. We prove that there is a strategy for the first player to build an arbitrarily long nonrepetitive sequence over 8 symbols. © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 2012pl
dc.affiliationWydział Matematyki i Informatyki : Zespół Katedr i Zakładów Informatyki Matematycznejpl
dc.contributor.authorGrytczuk, Jarosław - 128201 pl
dc.contributor.authorKozik, Jakub - 129355 pl
dc.contributor.authorMicek, Piotr - 142050 pl
dc.date.accessioned2014-07-16T05:09:41Z
dc.date.available2014-07-16T05:09:41Z
dc.date.issued2013pl
dc.description.number2pl
dc.description.physical214-225pl
dc.description.volume42pl
dc.identifier.doi10.1002/rsa.20411pl
dc.identifier.eissn1098-2418pl
dc.identifier.issn1042-9832pl
dc.identifier.urihttp://ruj.uj.edu.pl/xmlui/handle/item/56
dc.languageengpl
dc.language.containerengpl
dc.rights.licencebez licencji
dc.subtypeArticlepl
dc.titleNew approach to nonrepetitive sequencespl
dc.title.journalRandom Structures & Algorithmspl
dc.typeJournalArticlepl
dspace.entity.typePublication
cris.lastimport.scopus
2024-04-26T01:18:50Z
dc.abstract.enpl
A sequence is nonrepetitive if it does not contain two adjacent identical blocks. The remarkable construction of Thue asserts that three symbols are enough to build an arbitrarily long nonrepetitive sequence. It is still not settled whether the following extension holds: for every sequence of three-element sets L1,…,Ln there exists a nonrepetitive sequence s1,…,sn with si∈Li. We propose a new non-constructive way to build long nonrepetitive sequences and provide an elementary proof that sets of size 4 suffice confirming the best known bound. The simple double counting in the heart of the argument is inspired by the recent algorithmic proof of the Lovász local lemma due to Moser and Tardos. Furthermore we apply this approach and present game-theoretic type results on nonrepetitive sequences. Nonrepetitive game is played by two players who pick, one by one, consecutive terms of a sequence over a given set of symbols. The first player tries to avoid repetitions, while the second player, in contrast, wants to create them. Of course, by simple imitation, the second player can force lots of repetitions of size 1. However, as proved by Pegden, there is a strategy for the first player to build an arbitrarily long sequence over 37 symbols with no repetitions of size greater than 1. Our techniques allow to reduce 37–6. Another game we consider is the erase-repetition game. Here, whenever a repetition occurs, the repeated block is immediately erased and the next player to move continues the play. We prove that there is a strategy for the first player to build an arbitrarily long nonrepetitive sequence over 8 symbols. © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 2012
dc.affiliationpl
Wydział Matematyki i Informatyki : Zespół Katedr i Zakładów Informatyki Matematycznej
dc.contributor.authorpl
Grytczuk, Jarosław - 128201
dc.contributor.authorpl
Kozik, Jakub - 129355
dc.contributor.authorpl
Micek, Piotr - 142050
dc.date.accessioned
2014-07-16T05:09:41Z
dc.date.available
2014-07-16T05:09:41Z
dc.date.issuedpl
2013
dc.description.numberpl
2
dc.description.physicalpl
214-225
dc.description.volumepl
42
dc.identifier.doipl
10.1002/rsa.20411
dc.identifier.eissnpl
1098-2418
dc.identifier.issnpl
1042-9832
dc.identifier.uri
http://ruj.uj.edu.pl/xmlui/handle/item/56
dc.languagepl
eng
dc.language.containerpl
eng
dc.rights.licence
bez licencji
dc.subtypepl
Article
dc.titlepl
New approach to nonrepetitive sequences
dc.title.journalpl
Random Structures & Algorithms
dc.typepl
JournalArticle
dspace.entity.type
Publication

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