New results on pseudosquare avoidance

We start by considering binary words containing the minimum possible numbers of squares and antisquares (where an antisquare is a word of the form $x \overline{x}$), and we completely classify which possibilities can occur. We consider avoiding $x p(x)$, where $p$ is any permutation of the underlying alphabet, and $x t(x)$, where $t$ is any transformation of the underlying alphabet. Finally, we prove the existence of an infinite binary word simultaneously avoiding all occurrences of $x h(x)$ for every nonerasing morphism $h$ and all sufficiently large words $x$.

[1]  Leonid A. Levin,et al.  Complex tilings , 2001, STOC '01.

[2]  Aldo de Luca,et al.  Finiteness and Iteration Conditions for Semigroups , 1991, Theor. Comput. Sci..

[3]  Francine Blanchet-Sadri,et al.  Avoiding large squares in partial words , 2011, Theor. Comput. Sci..

[4]  Joseph S. Miller Two notes on subshifts , 2012 .

[5]  Maxime Crochemore,et al.  Fewest repetitions in infinite binary words , 2012, RAIRO Theor. Informatics Appl..

[6]  Zhi Xu,et al.  Pseudopower Avoidance , 2012, Fundam. Informaticae.

[7]  Antonio Restivo,et al.  Anti-Powers in Infinite Words , 2016, ICALP.

[8]  Maxim Ushakov,et al.  Forbidden Substrings, Kolmogorov Complexity and Almost Periodic Sequences , 2006, STACS.

[9]  R. C. ENTRINGER,et al.  On Nonrepetitive Sequences , 1974, J. Comb. Theory, Ser. A.

[10]  Dana Angluin,et al.  Finding Patterns Common to a Set of Strings , 1980, J. Comput. Syst. Sci..

[11]  Tero Harju,et al.  Binary Words with Few Squares , 2006, Bull. EATCS.

[12]  Jeffrey Shallit,et al.  Avoiding large squares in infinite binary words , 2003, Theor. Comput. Sci..

[13]  Pascal Ochem,et al.  A generator of morphisms for infinite words , 2006, RAIRO Theor. Informatics Appl..

[14]  Andrzej Ehrenfeucht,et al.  Finding a Homomorphism Between Two Words is NP-Complete , 1979, Inf. Process. Lett..

[15]  Hamoon Mousavi,et al.  Automatic Theorem Proving in Walnut , 2016, ArXiv.

[16]  Aviezri S. Fraenkel,et al.  How Many Squares Must a Binary Sequence Contain? , 1997, Electron. J. Comb..

[17]  Lucian Ilie,et al.  A generalization of repetition threshold , 2003, Theor. Comput. Sci..