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Over an alphabet of size 3 we construct an infinite balanced word with critical exponent 2+sqrt(2)/2. Over an alphabet of size 4 we construct an infinite balanced word with critical exponent (5+sqrt(5))/4. Over larger alphabets, we give…

Combinatorics · Mathematics 2018-01-17 Narad Rampersad , Jeffrey Shallit , Élise Vandomme

We study the threshold between avoidable and unavoidable repetitions in infinite balanced sequences over finite alphabets. The conjecture stated by Rampersad, Shallit and Vandomme says that the minimal critical exponent of balanced…

Combinatorics · Mathematics 2021-12-07 Lubomíra Dvořáková , Daniela Opočenská , Edita Pelantová , Arseny M. Shur

We find the lexicographically least infinite binary rich word having critical exponent $2+\sqrt{2}/2$

Formal Languages and Automata Theory · Computer Science 2023-10-12 James Currie , Narad Rampersad

We determine the minimum possible critical exponent for all palindromes over finite alphabets.

Formal Languages and Automata Theory · Computer Science 2016-12-21 Jeffrey Shallit

We study infinite ternary words that contain few distinct palindromes. In particular, we classify such words according to their critical exponent.

Combinatorics · Mathematics 2026-04-01 Ľubomíra Dvořáková , Lucas Mol , Pascal Ochem

For each $\alpha > 2$ there is a binary word with critical exponent $\alpha$.

Combinatorics · Mathematics 2009-04-14 James D. Currie , Narad Rampersad

A square is the concatenation of a nonempty word with itself. A word has period p if its letters at distance p match. The exponent of a nonempty word is the quotient of its length over its smallest period. In this article we give a proof of…

Discrete Mathematics · Computer Science 2012-07-25 Golnaz Badkobeh , Maxime Crochemore

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

We study infinite binary words that contain few distinct palindromes. In particular, we classify such words according to their critical exponents. This extends results by Fici and Zamboni [TCS 2013]. Interestingly, the words with 18 and 20…

Combinatorics · Mathematics 2024-03-27 L'ubomíra Dvořáková , Pascal Ochem , Daniela Opočenská

The exponent of a word is the ratio of its length over its smallest period. The repetitive threshold r(a) of an a-letter alphabet is the smallest rational number for which there exists an infinite word whose finite factors have exponent at…

Formal Languages and Automata Theory · Computer Science 2011-08-19 Golnaz Badkobeh , Maxime Crochemore

We investigate the least number of palindromic factors in an infinite word. We first consider general alphabets, and give answers to this problem for periodic and non-periodic words, closed or not under reversal of factors. We then…

Discrete Mathematics · Computer Science 2014-07-15 Gabriele Fici , Luca Q. Zamboni

We study aperiodic balanced sequences over finite alphabets. A sequence vv of this type is fully characterised by a Sturmian sequence u and two constant gap sequences y and y'. We show that the language of v is eventually dendric and we…

Formal Languages and Automata Theory · Computer Science 2022-10-21 Francesco Dolce , Lubomira Dvorakova , Edita Pelantova

The critical exponent of an infinite word is defined to be the supremum of the exponent of each of its factors. For k-automatic sequences, we show that this critical exponent is always either a rational number or infinite, and its value is…

Formal Languages and Automata Theory · Computer Science 2011-12-13 Luke Schaeffer , Jeffrey Shallit

A word of length $n$ is rich if it contains $n$ nonempty palindromic factors. An infinite word is rich if all of its finite factors are rich. Baranwal and Shallit produced an infinite binary rich word with critical exponent $2+\sqrt{2}/2$…

Combinatorics · Mathematics 2023-06-22 James D. Currie , Lucas Mol , Narad Rampersad

We revisit the question of classification of balanced circular words and focus on the case of a ternary alphabet. We propose a $3$-dimensional generalisation of the discrete approximation representation of Christoffel words. By considering…

Combinatorics · Mathematics 2021-05-03 D. V. Bulgakova , N. Buzhinsky , Y. O. Goncharov

In this paper, we study the critical exponent of infinite words $\ubeta$ coding $\beta$-integers for $\beta$ being a~non-simple Parry number. In other words, we investigate the maximal consecutive repetitions of factors that occur in the…

Combinatorics · Mathematics 2017-05-31 L. Balková , K. Klouda , E. Pelantová

A finite word $w\in\{0,1\}^*$ is balanced if for every equal-length factors $u$ and $v$ of every cyclic shift of $w$ we have $||u|_1-|v|_1| <= 1$. This new class of finite words were defined in [JZ]. In [J], there was proved several results…

Combinatorics · Mathematics 2015-01-16 Jetro Vesti

The (bitwise) complement $\overline{x}$ of a binary word $x$ is obtained by changing each $0$ in $x$ to $1$ and vice versa. An $\textit{antisquare}$ is a nonempty word of the form $x\, \overline{x}$. In this paper, we study infinite binary…

Combinatorics · Mathematics 2024-02-14 Aseem Baranwal , James Currie , Lucas Mol , Pascal Ochem , Narad Rampersad , Jeffrey Shallit

A position $p$ in a word $w$ is critical if the minimal local period at $p$ is equal to the global period of $w$. According to the Critical Factorisation Theorem all words of length at least two have a critical point. We study the number…

Combinatorics · Mathematics 2021-07-21 Tero Harju

Let G be an additive, finite abelian group. The critical number $\mathsf{cr}(G)$ of $G$ is the smallest positive integer $\ell$ such that for every subset $S \subset G \setminus \{0\}$ with $|S| \ge \ell$ the following holds: Every element…

Number Theory · Mathematics 2008-10-20 Michael Freeze , Weidong Gao , Alfred Geroldinger
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