21 research outputs found
Sur le défaut palindromique des mots infinis
Lorsqu'on s'intĂ©resse Ă l'Ă©tude de la structure combinatoire d'un mot infini w, une stratĂ©gie classique consiste Ă calculer sa fonction de complexitĂ©, c'est-Ă -dire Ă dĂ©crire le nombre de mots de longueur n qui apparaissent dans w, pour chaque entier n â„ 0. RĂ©cemment, des chercheurs se sont intĂ©ressĂ©s Ă un raffinement de cette notion en introduisant la fonction de complexitĂ© palindromique: pour chaque entier n â„ 0, nous calculons le nombre de palindromes de longueur n apparaissant dans w. Rappelons qu'un palindrome est un mot qui se lit de la mĂȘme façon de gauche Ă droite que de droite Ă gauche (par exemple, "radar" et "ressasser" sont des palindromes de la langue française). La connaissance des palindromes apparaissant dans un mot permet de dĂ©duire de nombreuses informations prĂ©cieuses sur sa structure. Par exemple, un mot admettant une infinitĂ© de palindromes prĂ©fixes est nĂ©cessairement rĂ©current (tout facteur apparaĂźt une infinitĂ© de fois) et son langage est fermĂ© sous l'opĂ©ration miroir. D'autre part, nous Ă©tudions Ă©galement les occurrences de facteurs antipalindromiques (une gĂ©nĂ©ralisation de la notion de palindrome), qui semblent naturellement en interaction avec les palindromes usuels. En particulier, nous dĂ©crivons les complexitĂ©s palindromique et antipalindromique de quelques familles importantes de mots: les mots pĂ©riodiques, les mots sturmiens, le mot de Thue-Morse et les suites de Rote. Dans un deuxiĂšme temps, nous Ă©tudions le dĂ©faut palindromique des mots finis et infinis. Il s'agit d'une mesure de "richesse" ou de "pauvretĂ©" en palindromes des mots. Nous montrons en particulier que certains mots associĂ©s aux suites de Rote, Ă l'instar des mots sturmiens (Droubay, Justin et Pirillo, 2001), sont aussi pleins, c'est-Ă -dire qu'ils rĂ©alisent la complexitĂ© palindromique maximale, et nous Ă©tablissons aussi des conditions sous lesquelles les mots pĂ©riodiques sont pleins. Une section supplĂ©mentaire est consacrĂ©e Ă l'Ă©tude des lacunes du mot de Thue-Morse, qui admet une infinitĂ© de palindromes, mais dont le dĂ©faut est infini (c'est-Ă -dire qu'il possĂšde une infinitĂ© de lacunes palindromiques). En dernier lieu, nous mentionnons quelques problĂšmes ouverts dans ce passionnant champ de recherche. ______________________________________________________________________________ MOTS-CLĂS DE LâAUTEUR : Combinatoire, Mots, Palindromes, Antipalindromes, ComplexitĂ©, DĂ©faut
On Words with the Zero Palindromic Defect
We study the set of finite words with zero palindromic defect, i.e., words
rich in palindromes. This set is factorial, but not recurrent. We focus on
description of pairs of rich words which cannot occur simultaneously as factors
of a longer rich word
Generalised Lyndon-SchĂŒtzenberger Equations
We fully characterise the solutions of the generalised Lyndon-SchĂŒtzenberger word equations , where for all , for all , for all , and is an antimorphic involution. More precisely, we show for which , , and such an equation has only -periodic solutions, i.e., , , and are in for some word , closing an open problem by Czeizler et al. (2011)
An Optimal Algorithm for Tiling the Plane with a Translated Polyomino
We give a -time algorithm for determining whether translations of a
polyomino with edges can tile the plane. The algorithm is also a
-time algorithm for enumerating all such tilings that are also regular,
and we prove that at most such tilings exist.Comment: In proceedings of ISAAC 201
Repetitions in infinite palindrome-rich words
Rich words are characterized by containing the maximum possible number of
distinct palindromes. Several characteristic properties of rich words have been
studied; yet the analysis of repetitions in rich words still involves some
interesting open problems. We address lower bounds on the repetition threshold
of infinite rich words over 2 and 3-letter alphabets, and construct a candidate
infinite rich word over the alphabet with a small critical
exponent of . This represents the first progress on an open
problem of Vesti from 2017.Comment: 12 page
The impact of managerial characteristics on business strategies under the environmental change: an investigation of the Israeli diamond industry
The changing business environment has required firms to adopt
new strategies to facilitate efficient organizational adaptation.
Previous upper echelons studies suggested that the demographic
characteristics of top managers influence their choice of strategies, and ultimately the firmsâ performance. These studies tended
to examine firms in a homogenous way. The characteristics of
family-owned firms, together with the unique external environment within which they operate, have been largely ignored. This
study aims to fill this gap and examine the relationships between
the top managersâ characteristics and their choice of exchange
strategy within the diamond industry in light of the environmental changes. This paper illustrates the evolutionary stages of the
diamond industry and how players adjust their strategies in-line
with the environment. We interviewed 100 diamond firm managers to gather the empirical data. The results have shown that certain managerial characteristics, such as family background and
marketing experience, have positively influenced the choice of
using the armâs length market exchange strategies. Our findings
have also reflected that the relationship between managersâ characteristics and strategic choice is social and normative. Many
managers follow the family or community traditions and imitate
other key industry players in order to achieve legitimacy from the
stakeholders and improve competitiveness
Two infinite families of polyominoes that tile the plane by translation in two distinct ways
On the critical exponent of generalized Thue-Morse sequences
For certain generalized Thue-Morse words t, we compute the "critical exponent", i.e., the supremum of the set of rational numbers that are exponents of powers in t, and determine exactly the occurrences of powers realizing it