Square network on a word
Square network on a word
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DOI:
10.1016/j.tcs.2021.08.004
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发表时间:
2021
影响因子:
1.1
通讯作者:
Seki Shinnosuke
中科院分区:
文献类型:
--
作者:
Fazekas Szilard Zsolt;Seki Shinnosuke
Left-aligned last occurrences of squares (double-square) have provided profound insights into the question of how many distinct squares can be packed on a word ω of length n and brought the best known upper bound 11 n/6. Other types of alignments such as being center-aligned as well as long distance relations such as being the occurrences of the same square incorporate the squares on ω into a bipartite graph of the squares and positions {1, 2,…, n}, which we call the square network. Packing more and more squares in a limited space certainly induces specific kinds of subgraphs once the square density exceeds a threshold, and if one of the subgraphs is known to be forbidden, the threshold provides an upper bound on the number of distinct squares. In this paper, we designate a specific position of double-squares as P 1 and obtain certain induced subgraphs as well as forbidden ones guaranteed by the presence of P 1-aligned double squares; an induced subgraph of particular interest expresses the global uniqueness of squares involved.