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A word is called closed if it has a prefix which is also its suffix and there is no internal occurrences of this prefix in the word. In this paper we study words that are rich in closed factors, i.e., which contain the maximal possible…

Combinatorics · Mathematics 2023-01-05 Olga Parshina , Svetlana Puzynina

We study a class of functional problems reducible to computing $f^{(n)}(x)$ for inputs $n$ and $x$, where $f$ is a polynomial-time bijection. As we prove, the definition is robust against variations in the type of reduction used in its…

Computational Complexity · Computer Science 2024-02-14 David Eppstein

We provide an exact estimate on the maximal subword complexity for quasiperiodic infinite words. To this end we give a representation of the set of finite and of infinite words having a certain quasiperiod q via a finite language derived…

Formal Languages and Automata Theory · Computer Science 2010-08-11 Ronny Polley , Ludwig Staiger

In this paper we introduce and study a family of complexity functions of infinite words indexed by $k \in \ints ^+ \cup {+\infty}.$ Let $k \in \ints ^+ \cup {+\infty}$ and $A$ be a finite non-empty set. Two finite words $u$ and $v$ in $A^*$…

Combinatorics · Mathematics 2013-01-23 Juhani Karhumaki , Aleksi Saarela , Luca Q. Zamboni

In this article, we show that the Kamae-Xue complexity function for an infinite sequence classifies eventual periodicity completely. We prove that an infinite binary word $x_1x_2 \cdots $ is eventually periodic if and only if…

Computational Complexity · Computer Science 2014-04-18 Teturo Kamae , Dong Han Kim

We prove an isomorphism between the finite domain from 1 up to the product of the first n primes and the new defined set of prime modular numbers. This definition provides some insights about relative prime numbers. We provide an inverse…

Number Theory · Mathematics 2014-05-23 Matthias Schmitt

The automatic complexity of a finite word (string) is an analogue for finite automata of Sipser's distinguishing complexity (1983) and was introduced by Shallit and Wang (2001). For a finite alphabet $\Sigma$ of at least two elements, we…

Formal Languages and Automata Theory · Computer Science 2025-10-10 Joey Chen , Bjørn Kjos-Hanssen , Ivan Koswara , Linus Richter , Frank Stephan

Given a finite alphabet $\Sigma$ and a right-infinite word $\bf w$ over $\Sigma$, we define the Lie complexity function $L_{\bf w}:\mathbb{N}\to \mathbb{N}$, whose value at $n$ is the number of conjugacy classes (under cyclic shift) of…

Formal Languages and Automata Theory · Computer Science 2021-02-09 Jason P. Bell , Jeffrey Shallit

Regular episturmian words are episturmian words whose directive words have a regular and restricted form making them behave more like Sturmian words than general episturmian words. We present a method to evaluate the initial nonrepetitive…

Formal Languages and Automata Theory · Computer Science 2024-03-28 Jarkko Peltomäki

We analyze the algorithm in [Holub, 2009], which decides whether a given word is a fixed point of a nontrivial morphism. We show that it can be implemented to have complexity in O(mn), where n is the length of the word and m the size of the…

Formal Languages and Automata Theory · Computer Science 2013-10-04 Vojtěch Matocha , Štěpán Holub

The critical exponent of an infinite word $\bf x$ is the supremum, over all finite nonempty factors $f$, of the exponent of $f$. In this note we show that for all integers $k\geq 2,$ there is a binary infinite $k$-automatic sequence with…

Combinatorics · Mathematics 2026-02-25 J. -P. Allouche , N. Rampersad , J. Shallit

The number of frequencies of factors of length $n+1$ in a recurrent aperiodic infinite word does not exceed $3\Delta \C(n)$, where $\Delta \C (n)$ is the first difference of factor complexity, as shown by Boshernitzan. Pelantov\'a together…

Combinatorics · Mathematics 2013-02-05 Lubomira Balkova

In this paper we investigate local to global phenomena for a new family of complexity functions of infinite words indexed by $k \in \Ni \cup \{+\infty\}$ where $\Ni$ denotes the set of positive integers. Two finite words $u$ and $v$ in…

Combinatorics · Mathematics 2013-02-18 Juhani Karhumäki , Aleksi Saarela , Luca. Q. Zamboni

We study how much injective morphisms can increase the repetitiveness of a given word. This question has a few possible variations depending on the meaning of ``repetitiveness''. We concentrate on fractional exponents of finite words and…

Combinatorics · Mathematics 2025-06-06 Eva Foster , Aleksi Saarela , Aleksi Vanhatalo

Partial words are sequences over a finite alphabet that may contain wildcard symbols, called holes, which match or are compatible with all letters; partial words without holes are said to be full words (or simply words). Given an infinite…

Discrete Mathematics · Computer Science 2011-08-19 Francine Blanchet-Sadri , Aleksandar Chakarov , Lucas Manuelli , Jarett Schwartz , Slater Stich

Let us consider an infinite word and $k\geq 1$ an integer. By steps of $k$, we substitute a letter ofthis infinite word by the power of an external letter. The new word obtaining by this process is called $k$ to $k$ substitution of a power…

Combinatorics · Mathematics 2024-05-31 Moussa Barro , K. Ernest Bognini , Boucaré Kientéga

The notion of string attractor has been introduced in [Kempa and Prezza, 2018] in the context of Data Compression and it represents a set of positions of a finite word in which all of its factors can be "attracted". The smallest size…

Formal Languages and Automata Theory · Computer Science 2022-06-02 Antonio Restivo , Giuseppe Romana , Marinella Sciortino

In this paper, we investigate the combinatorial and density properties of infinite words generated by Fibonacci-type morphisms, focusing on their subword structure, palindrome density, and extremal statistical behaviors. Using the morphism…

Combinatorics · Mathematics 2026-01-21 Duaa Abdullah , Jasem Hamoud

In previous papers, for an arithmetical function $f_0$, we defined functions $f_m$ and $c_m$ and designated numbers of restricted words over a finite alphabet counted by these functions. In this paper, we examine the reverse problem for…

Combinatorics · Mathematics 2017-06-02 Milan Janjic

Combinatorial properties of maximal repetitions (runs) in formal words are studied. We classify all maximal repetitions in a word as primary and secondary where the set of all primary repetitions determines all the other repetitons in the…

Formal Languages and Automata Theory · Computer Science 2011-03-29 Roman Kolpakov