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Register a new userOn abelian and additive complexity in infinite words
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The study of the structure of infinite words having bounded abelian complexity was initiated by G. Richomme, K. Saari, and L. Q. Zamboni. In this note we define bounded additive complexity for infinite words over a finite subset of Z^m. We provide an alternative proof of one of the results of Richomme, Saari, and Zamboni.
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A universal word for a finite alphabet $A$ and some integer $ngeq 1$ is a word over $A$ such that every word in $A^n$ appears exactly once as a subword (cyclically or linearly). It is well-known and easy to prove that universal words exist for any $A$ and $n$. In this work we initiate the systematic study of universal partial words. These are words that in addition to the letters from $A$ may contain an arbitrary number of occurrences of a special `joker symbol $Diamond otin A$, which can be substituted by any symbol from $A$. For example, $u=0Diamond 011100$ is a linear partial word for the binary alphabet $A={0,1}$ and for $n=3$ (e.g., the first three letters of $u$ yield the subwords $000$ and $010$). We present results on the existence and non-existence of linear and cyclic universal partial words in different situations (depending on the number of $Diamond$s and their positions), including various explicit constructions. We also provide numerous examples of universal partial words that we found with the help of a computer.
Stankova and West showed that for any non-negative integer $s$ and any permutation $gamma$ of ${4,5,dots,s+3}$ there are as many permutations that avoid $231gamma$ as there are that avoid $312gamma$. We extend this result to the setting of words.
We present results on the existence of long arithmetic progressions in the Thue-Morse word and in a class of generalised Thue-Morse words. Our arguments are inspired by van der Waerdens proof for the existence of arbitrary long monochromatic arithmetic progressions in any finite colouring of the (positive) integers.
Let S be a double occurrence word, and let M_S be the words interlacement matrix, regarded as a matrix over GF(2). Gauss addressed the question of which double occurrence words are realizable by generic closed curves in the plane. We reformulate answers given by Rosenstiehl and by de Fraysseix and Ossona de Mendez to give new graph-theoretic and algebraic characterizations of realizable words. Our algebraic characterization is especially pleasing: S is realizable if and only if there exists a diagonal matrix D_S such that M_S+D_S is idempotent over GF(2).
In this paper, we investigate statistics on alternating words under correspondence between ``possible reflection paths within several layers of glass and ``alternating words. For $v=(v_1,v_2,cdots,v_n)inmathbb{Z}^{n}$, we say $P$ is a path within $n$ glass plates corresponding to $v$, if $P$ has exactly $v_i$ reflections occurring at the $i^{rm{th}}$ plate for all $iin{1,2,cdots,n}$. We give a recursion for the number of paths corresponding to $v$ satisfying $v in mathbb{Z}^n$ and $sum_{igeq 1} v_i=m$. Also, we establish recursions for statistics around the number of paths corresponding to a given vector $vinmathbb{Z}^n$ and a closed form for $n=3$. Finally, we give a equivalent condition for the existence of path corresponding to a given vector $v$.
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