A Counterexample to a Question of Hof, Knill and Simon
نویسنده
چکیده
In this article, we give a negative answer to a question of Hof, Knill and Simon (1995) concerning purely morphic sequences obtained from primitive morphism containing an infinite number of palindromes. Their conjecture states that such palindromic sequences arise from substitutions that are in class P. The conjecture was proven for the binary alphabet by B. Tan in 2007. We give here a counterexample for a ternary alphabet.
منابع مشابه
Mirror substitutions and palindromic sequences
By introducing the notion of mirror substitution, we show that, given a substitutive sequence over two letters, it is palindromic (that is, it contains arbitrarily long palindromes) if and only if its language is mirror-invariant (that is, it is closed under the mirror image map). Then we solve a question of Hof, Knill and Simon in the 2-letter case, and also, by constructing a counterexample, ...
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ورودعنوان ژورنال:
- Electr. J. Comb.
دوره 21 شماره
صفحات -
تاریخ انتشار 2014