a first investigation of sturmian trees
play

A First Investigation of Sturmian Trees Jean Berstel 2 , Luc Boasson - PowerPoint PPT Presentation

A First Investigation of Sturmian Trees Jean Berstel 2 , Luc Boasson 1 Olivier Carton 1 , Isabelle Fagnot 2 1 LIAFA, CNRS Universit e Paris 7 2 IGM, CNRS Universit e de Marne-la-Vall ee STACS2007, Aachen Olivier Carton (LIAFA)


  1. A First Investigation of Sturmian Trees Jean Berstel 2 , Luc Boasson 1 Olivier Carton 1 , Isabelle Fagnot 2 1 LIAFA, CNRS Universit´ e Paris 7 2 IGM, CNRS Universit´ e de Marne-la-Vall´ ee STACS’2007, Aachen Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 1 / 14

  2. Outline 1 Sturmian words 2 Sturmian trees 3 Slow automata 4 Rank and degree 5 Results Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 2 / 14

  3. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  4. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a a aa aab aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  5. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b b ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  6. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  7. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa aabab ba ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  8. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aa aab aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  9. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  10. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  11. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa aabab ba baa baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  12. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aab aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  13. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  14. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  15. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  16. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab baab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  17. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  18. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa aabab ba baa abab abab abaab Factors bab baab ababa baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  19. Factors of an infinite word A factor w of a word x is a finite word that occurs in x , that is, there are words u and y such that x = uwy . Example (Fibonacci word) x = a b a a b a b a a b a a b a b a a b a b a a b . . . Length: n 1 2 3 4 5 a aa aab aaba aabaa b ab aba abaa aabab ba baa abab abaab Factors bab baab ababa baba baba baaba babaa # 2 3 4 5 6 Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 3 / 14

  20. Sturmian words Proposition (Hedlund & Morse) An infinite word x ultimately periodic iff there is an integer n such that x has at most n distinct factors of length n . An infinite word x is Sturmian if the number of its factors of length n is n + 1 for each n . Sturmian words are non ultimately periodic words with the smallest complexity. Example (Fibonacci word: f n +2 = f n +1 f n ) f 0 = a f 1 = ab f 2 = aba f 3 = abaab f ω = abaababa · · · Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 4 / 14

  21. Characterization: cutting sequences y = βx + ρ x = a b b a b ab b a b ba b Theorem A infinite word is Sturmian iff it is the cutting sequence of a straight line y = βx + ρ with an irrational slope β . Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 5 / 14

  22. Factor of a tree A factor of height h of a tree t is a subtree of height h that occurs in t . • • • Factor • • • • of height 3 • • • • • • • • Factor of height 2 • • • • • • • • • • • • • • • • Olivier Carton (LIAFA) Sturmian Trees STACS’2007, Aachen 6 / 14

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend