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Following (Kolpakov et al., 2013; Gawrychowski and Manea, 2015), we continue the study of {\em $\alpha$-gapped repeats} in strings, defined as factors $uvu$ with $|uv|\leq \alpha |u|$. Our main result is the $O(\alpha n)$ bound on the…

Formal Languages and Automata Theory · Computer Science 2015-10-05 Maxime Crochemore , Roman Kolpakov , Gregory Kucherov

A finite word $w$ of length $n$ contains at most $n+1$ distinct palindromic factors. If the bound $n+1$ is attained, the word $w$ is called rich. An infinite word $w$ is called rich if every finite factor of $w$ is rich. Let $w$ be a word…

Combinatorics · Mathematics 2021-01-21 Josef Rukavicka

A {\em subsequence} of a word $w$ is a word $u$ that can be obtained by deleting some letters from $w$ while maintaining the relative order of the remaining letters, e.g., $\mathtt{lala}$ is a subsequence of $\mathtt{alfalfa}$. A word, over…

Formal Languages and Automata Theory · Computer Science 2025-09-01 Duncan Adamson , Pamela Fleischmann , Annika Huch , Florin Manea , Paul Sarnighausen-Cahn , Max Wiedenhöft

It is commonly believed that the normalized gaps between consecutive ordinates $t_n$ of the zeros of the Riemann zeta function on the critical line can be arbitrarily large. In particular, drawing on analogies with random matrix theory, it…

Number Theory · Mathematics 2017-05-29 André LeClair

Suppose that $[n]=\left\{0,1,2,...,n\right\}$ is a set of non-negative integers and $h,k \in [n]$. The $L(h,k)$-labeling of graph $G$ is the function $l:V(G)\rightarrow[n]$ such that $\left|l(u)-l(v)\right|\geq h$ if the distance $d(u,v)$…

Combinatorics · Mathematics 2014-01-30 Deborah O. A. Ajayi , Tayo C. Adefokun

A \emph{morphism} is a mapping that transforms words through letter-wise substitution, where each symbol is consistently replaced by a fixed word. In the field of combinatorics on words, one topic that has attracted considerable attention…

Combinatorics · Mathematics 2026-05-19 Kaisei Kishi , Peaker Guo , Cristian Urbina , Hideo Bannai

The prefix palindromic length $p_{\mathbf{u}}(n)$ of an infinite word $\mathbf{u}$ is the minimal number of concatenated palindromes needed to express the prefix of length $n$ of $\mathbf{u}$. This function is surprisingly difficult to…

Combinatorics · Mathematics 2022-03-15 Dora V. Bulgakova , Anna E. Frid , Jérémy Scanvic

Two finite words $u$ and $v$ are called abelian equivalent if each letter occurs equally many times in both $u$ and $v$. The abelian closure $\mathcal{A}(\mathbf{x})$ of an infinite word $\mathbf{x}$ is the set of infinite words…

Combinatorics · Mathematics 2021-01-01 Juhani Karhumäki , Svetlana Puzynina , Markus A. Whiteland

We study invariant measures for random countable (finite or infinite) conformal iterated function systems (IFS) with arbitrary overlaps. We do not assume any type of separation condition. We prove, under a mild assumption of finite entropy,…

Dynamical Systems · Mathematics 2015-03-24 Eugen Mihailescu , Mariusz Urbanski

Let u be a cyclic word in a free group F_n of finite rank n that has the minimum length over all cyclic words in its automorphic orbit, and let N(u) be the cardinality of the set {v: |v|=|u| and v= \phi(u) for some \phi \in \text {Aut}F_n}.…

Group Theory · Mathematics 2011-05-03 Donghi Lee

The power graph $\Gamma_G$ of a finite group $G$ is the graph with the vertex set $G$, where two distinct elements are adjacent if one is a power of the other. An $L(2, 1)$-labeling of a graph $\Gamma$ is an assignment of labels from…

Combinatorics · Mathematics 2017-08-01 Xuanlong Ma , Min Feng , Kaishun Wang

Let $L_{K}(A)$ be the free Lie algebra on a finite alphabet $A$ over a commutative ring $K$ with unity. For a word $u$ in the free monoid $A^{*}$ let $\tilde{u}$ denote its reversal. Two words in $A^{*}$ are called twin (resp. anti-twin) if…

Combinatorics · Mathematics 2010-11-09 Ioannis C. Michos

In [97,99,100], an fl-RDT framework is introduced to characterize \emph{statistical computational gaps} (SCGs). Studying \emph{symmetric binary perceptrons} (SBPs), [100] obtained an \emph{algorithmic} threshold estimate $\alpha_a\approx…

Machine Learning · Computer Science 2026-04-22 Mihailo Stojnic

In recent years, deep learning-based sequence modelings, such as language models, have received much attention and success, which pushes researchers to explore the possibility of transforming non-sequential problems into a sequential form.…

Machine Learning · Computer Science 2024-05-24 Yongqiang Cai

The observed frequency of the longest proper prefix, the longest proper suffix, and the longest infix of a word $w$ in a given sequence $x$ can be used for classifying $w$ as avoided or overabundant. The definitions used for the expectation…

We show that the first-order logical theory of the binary overlap-free words (and, more generally, the ${\alpha}$-free words for rational ${\alpha}$, $2 < {\alpha} \leq 7/3$), is decidable. As a consequence, many results previously obtained…

Formal Languages and Automata Theory · Computer Science 2022-09-08 L. Schaeffer , J. Shallit

In this paper we study the asymptotic behaviour of two relatively new complexity functions defined on infinite words and their relationship to periodicity. Given a factor $u$ of an infinite word $x$, we say $u$ is closed if it is a letter…

Combinatorics · Mathematics 2023-01-04 O. Parshina , M. Postic

An absent word of a word y of length n is a word that does not occur in y. It is a minimal absent word if all its proper factors occur in y. Minimal absent words have been computed in genomes of organisms from all domains of life; their…

Data Structures and Algorithms · Computer Science 2014-07-01 Carl Barton , Alice Heliou , Laurent Mouchard , Solon P. Pissis

A subsequence of a word $w$ is a word $u$ such that $u = w[i_1] w[i_2] \dots w[i_{k}]$, for some set of indices $1 \leq i_1 < i_2 < \dots < i_k \leq \lvert w\rvert$. A word $w$ is $k$-subsequence universal over an alphabet $\Sigma$ if every…

Formal Languages and Automata Theory · Computer Science 2023-11-20 Duncan Adamson , Pamela Fleischmann , Annika Huch , Tore Koß , Florin Manea , Dirk Nowotka

An overlap representation is an assignment of sets to the vertices of a graph in such a way that two vertices are adjacent if and only if the sets assigned to them overlap. The overlap number of a graph is the minimum number of elements…

Discrete Mathematics · Computer Science 2010-08-17 Bill Rosgen , Lorna Stewart