46,843 research outputs found
On the number of return words in infinite words with complexity 2n+1
In this article, we count the number of return words in some infinite words
with complexity 2n+1. We also consider some infinite words given by codings of
rotation and interval exchange transformations on k intervals. We prove that
the number of return words over a given word w for these infinite words is
exactly k.Comment: see also http://liafa.jussieu.fr/~vuillon/articles.htm
Interval exchanges, admissibility and branching Rauzy induction
We introduce a definition of admissibility for subintervals in interval
exchange transformations. Using this notion, we prove a property of the natural
codings of interval exchange transformations, namely that any derived set of a
regular interval exchange set is a regular interval exchange set with the same
number of intervals. Derivation is taken here with respect to return words. We
characterize the admissible intervals using a branching version of the Rauzy
induction. We also study the case of regular interval exchange transformations
defined over a quadratic field and show that the set of factors of such a
transformation is primitive morphic. The proof uses an extension of a result of
Boshernitzan and Carroll
On morphisms preserving palindromic richness
It is known that each word of length contains at most distinct
palindromes. A finite rich word is a word with maximal number of palindromic
factors. The definition of palindromic richness can be naturally extended to
infinite words. Sturmian words and Rote complementary symmetric sequences form
two classes of binary rich words, while episturmian words and words coding
symmetric -interval exchange transformations give us other examples on
larger alphabets. In this paper we look for morphisms of the free monoid, which
allow to construct new rich words from already known rich words. We focus on
morphisms in Class . This class contains morphisms injective on the
alphabet and satisfying a particular palindromicity property: for every
morphism in the class there exists a palindrome such that
is a first complete return word to for each letter . We
characterize morphisms which preserve richness over a binary
alphabet. We also study marked morphisms acting on alphabets with
more letters. In particular we show that every Arnoux-Rauzy morphism is
conjugated to a morphism in Class and that it preserves richness
Return words of linear involutions and fundamental groups
We investigate the natural codings of linear involutions. We deduce from the
geometric representation of linear involutions as Poincar\'e maps of measured
foliations a suitable definition of return words which yields that the set of
first return words to a given word is a symmetric basis of the free group on
the underlying alphabet . The set of first return words with respect to a
subgroup of finite index of the free group on is also proved to be a
symmetric basis of
Geodesics on Flat Surfaces
This short survey illustrates the ideas of Teichmuller dynamics. As a model
application we consider the asymptotic topology of generic geodesics on a
"flat" surface and count closed geodesics and saddle connections. This survey
is based on the joint papers with A.Eskin and H.Masur and with M.Kontsevich.Comment: (25 pages, 5 figures) Based on the talk at ICM 2006 at Madrid; see
Proceedings of the ICM, Madrid, Spain, 2006, EMS, 121-146 for the final
version. For a more detailed survey see the paper "Flat Surfaces",
arXiv.math.DS/060939
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