| Issue |
RAIRO-Theor. Inf. Appl.
Volume 48, Number 4, October-December 2014
Special issue in the honor of the 14th "Journées Montoises d'Informatique Théorique". II.
|
|
|---|---|---|
| Page(s) | 419 - 430 | |
| DOI | https://doi.org/10.1051/ita/2014017 | |
| Published online | 11 August 2014 | |
Finite repetition threshold for large alphabets
1 King’s, College London, UK. ;
golnaz.badkobeh@kcl.ac.uk
2 Université Paris-Est, 77454 Marne-la-Vallée, France.
3 LIP, CNRS, ENS de Lyon, UCBL, Université de Lyon, France.
michael.rao@ens-lyon.fr
Received: 14 March 2014
Accepted: 17 March 2014
We investigate the finite repetition threshold for k-letter alphabets, k ≥ 4, that is the smallest number r for which there exists an infinite r+-free word containing a finite number of r-powers. We show that there exists an infinite Dejean word on a 4-letter alphabet (i.e. a word without factors of exponent more than 7/5 ) containing only two 7/5 -powers. For a 5-letter alphabet, we show that there exists an infinite Dejean word containing only 60 5/4 -powers, and we conjecture that this number can be lowered to 45. Finally we show that the finite repetition threshold for k letters is equal to the repetition threshold for k letters, for every k ≥ 6.
Mathematics Subject Classification: 68R15
Key words: Morphisms / repetitions in words / Dejean’s threshold
© EDP Sciences 2014
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