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We consider involutory antimorphisms ϑ of a free monoid A * and their fixed points, called ϑ-palindromes or pseudopalindromes. A ϑ-palindrome reduces to a usual palindrome when ϑ is the reversal operator. For any word w ∈ A * the right (resp. left) ϑ-palindrome closure of w is the shortest ϑ-palindrome having w as a prefix (resp. suffix). We prove some(More)
In this paper we solve some open problems related to (pseudo)pal-indrome closure operators and to the infinite words generated by their iteration, that is, standard episturmian and pseudostandard words. We show that if ϑ is an involutory antimorphism of A * , then both ϑ-palindromic closures of any factor of a ϑ-standard word are also factors of some(More)
In this paper we consider the following question in the spirit of Ramsey theory: Given x ∈ A ω , where A is a finite non-empty set, does there exist a finite coloring of the non-empty factors of x with the property that no factorization of x is monochromatic? We prove that this question has a positive answer using two colors for almost all words relative to(More)