Abstract
The Parikh matrix, an extension of the Parikh vector for words, is a fundamental concept in combinatorics on words. We investigate M-unambiguity that identifies words with unique Parikh matrices. While the problem of identifying M-unambiguous words for a binary alphabet is solved using a palindromicly amicable relation, it is open for larger alphabets. We propose substitution rules that establish M-equivalence and solve the problem of M-unambiguity for a ternary alphabet. Our rules build on the principles of the palindromicly amicable relation and enable tracking of the differences of length-3 ordered scattered-factors. We characterize the set of M-unambiguous words and obtain a regular expression for the set.
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Acknowledgments
We thank all the reviewers for their valuable comments. This research was supported by the NRF grant funded by MIST (NRF-RS-2023-00208094). The first two authors contributed equally.
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Hahn, J., Cheon, H., Han, YS. (2023). M-equivalence of Parikh Matrix over a Ternary Alphabet. In: Nagy, B. (eds) Implementation and Application of Automata. CIAA 2023. Lecture Notes in Computer Science, vol 14151. Springer, Cham. https://doi.org/10.1007/978-3-031-40247-0_10
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DOI: https://doi.org/10.1007/978-3-031-40247-0_10
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