Abstract
We study growth properties of power-free languages over finite alphabets. We consider the function α(k,β) whose values are the exponential growth rates of β-power-free languages over k-letter alphabets and clarify its asymptotic behaviour. Namely, we prove asymptotic formulas for this function for the case β≥2 and suggest such formulas for the case β<2 on the base of some partial results. All obtained formulas correlate very well with the known numerical bounds on the values of α(k,β).
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Notes
Apart from the case a=n+s=k which is also consistent with the general pattern.
References
Berstel, J.: Growth of repetition-free words—a review. Theor. Comput. Sci. 340, 280–290 (2005)
Berstel, J., Karhumäki, J.: Combinatorics on words: a tutorial. Bull. Eur. Assoc. Theor. Comput. Sci. 79, 178–228 (2003)
Brandenburg, F.-J.: Uniformly growing k-th power free homomorphisms. Theor. Comput. Sci. 23, 69–82 (1983)
Carpi, A.: On Dejean’s conjecture over large alphabets. Theor. Comput. Sci. 385, 137–151 (2007)
Crochemore, M., Mignosi, F., Restivo, A.: Automata and forbidden words. Inf. Process. Lett. 67(3), 111–117 (1998)
Currie, J.D., Rampersad, N.: Dejean’s conjecture holds for n≥27, RAIRO. Inform. Théor. Appl. 43, 775–778 (2009)
Currie, J.D., Rampersad, N.: A proof of Dejean’s conjecture. Math. Comput. 80, 1063–1070 (2011)
Cvetković, D.M., Doob, M., Sachs, H.: Spectra of Graphs. Theory and Applications, 3rd edn. Johann Ambrosius Barth, Heidelberg (1995)
Dejean, F.: Sur un theoreme de Thue. J. Comb. Theory, Ser. A 13(1), 90–99 (1972)
Gantmacher, F.R.: Application of the Theory of Matrices. Interscience, New York (1959)
Lothaire, M.: Combinatorics on Words. Addison-Wesley, Reading (1983)
Morse, M., Hedlund, G.A.: Symbolic dynamics. Am. J. Math. 60, 815–866 (1938)
Rao, M.: Last cases of Dejean’s conjecture. Theor. Comput. Sci. 412, 3010–3018 (2011)
Shur, A.M.: Comparing complexity functions of a language and its extendable part. RAIRO Theor. Inform. Appl. 42, 647–655 (2008)
Shur, A.M.: Combinatorial complexity of regular languages. In: Proc. 3rd International Computer Science Symposium in Russia, LNCS, vol. 5010, pp. 289–301. Springer, Berlin (2008)
Shur, A.M.: Growth rates of complexity of power-free languages. Theor. Comput. Sci. 411, 3209–3223 (2010)
Shur, A.M.: Two-sided bounds for the growth rates of power-free languages. In: Developments in Language Theory 2009, LNCS, vol. 5583, pp. 466–477. Springer, Berlin (2009)
Shur, A.M.: On the existence of minimal β-powers. In: Developments in Language Theory 2010, LNCS, vol. 6224, pp. 411–422. Springer, Berlin (2010)
Shur, A.M., Gorbunova, I.A.: On the growth rates of complexity of threshold languages. RAIRO Theor. Inform. Appl. 44, 175–192 (2010)
Thue, A.: Über unendliche Zeichenreihen. Kra. Vidensk. Selsk. Skrifter. I. Mat.-Nat. Kl., Christ. 7, 1–22 (1906)
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Shur, A.M. Growth of Power-Free Languages over Large Alphabets. Theory Comput Syst 54, 224–243 (2014). https://doi.org/10.1007/s00224-013-9512-x
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DOI: https://doi.org/10.1007/s00224-013-9512-x