Abstract
The introduction of Parikh matrices by Mateescu et al. in 2001 has sparked numerous new investigations in the theory of formal languages by various researchers, among whom is Şerbănuţă. Recently, a decade-old conjecture by Şerbǎnuţǎ on the M-ambiguity of words has disproved, leading to new possibilities in the study of such words. In this paper, we investigate how selective repeated duplications of letters in a word affect the M-ambiguity of the resulting words. The corresponding M-ambiguity of each of those words is then presented in sequences, which we term as M-ambiguity sequences. We show that nearly all patterns of M-ambiguity sequences are attainable. Finally, by employing certain algebraic approach and some underlying theory in integer programming, we show that repeated periodic duplications of letters of the same type in a word result in an M-ambiguity sequence that is ultimately periodic.
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Notes
See Theorem A.1 in [16].
It will be clear why each \(u_i\) is a letter instead of a word when the reader reaches the second sentence of the next paragraph.
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Acknowledgements
The authors would like to thank the anonymous referees for their careful reading of the original version of this paper. Their comments and suggestions have significantly improved the clarity of the work presented here. The authors also gratefully acknowledge support for this research by a Research University Grant No. 1001/PMATHS/8011019 of Universiti Sains Malaysia. This study is an extension of the work in [11].
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Communicated by Rosihan M. Ali.
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Poovanandran, G., Teh, W.C. M-ambiguity Sequences for Parikh Matrices and Their Periodicity Revisited. Bull. Malays. Math. Sci. Soc. 43, 3305–3321 (2020). https://doi.org/10.1007/s40840-019-00867-w
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DOI: https://doi.org/10.1007/s40840-019-00867-w