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arXiv 1001.0797math.CO
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关于全控制点临界图的存在性问题

On the existence problem of the total domination vertex critical graphs

Moo Young Sohn, Dongseok Kim, Young Soo Kwon, Jaeun Lee

摘要:

关于全控制点临界图的存在性问题,已有一系列的文章进行了研究。本条的目的有两个。首先,我们解决了关于全控制数m和最大度Delta的奇偶性的存在性问题:对于除m=4以外的偶数m,不存在m-γ_t-临界图,而不管Delta的奇偶性如何;对于m=4或奇数m \ge 3,对于偶数Delta,存在m-γ_t-临界图当且仅当Delta \ge 2 \lfloor \frac{m-1}{2} \rfloor ;对于m=4或奇数m \ge 3,对于奇数Delta,如果Delta \ge 2 \lfloor \frac{m-1}{2} \rfloor +7,则存在m-gamma_t-临界图,如果Delta < 2 \lfloor \frac{m-1}{2} \rfloor,则不存在m-gamma_t-临界图。仅有的剩余开放情况是Delta = 2 \lfloor \frac{m-1}{2} \rfloor +k,k=1,3,5。第二,我们研究这些剩余的开放的情况下,当m=4或奇数m \ge 9。作为m = 3的已知结果,我们还证明了对于Delta(G)= 3,5,7,不存在阶为Delta(G)+4的4-gamma_t-临界图.相反,它表明,对于奇数m \ge 9存在一个m-gamma_t-临界图的所有德尔塔\ge m-1。

英文摘要:

The existence problem of the total domination vertex critical graphs has been studied in a series of articles. The aim of the present article is twofold. First, we settle the existence problem with respect to the parities of the total domination number m and the maximum degree Delta : for even m except m=4, there is no m-gamma_t-critical graph regardless of the parity of Delta; for m=4 or odd m \ge 3 and for even Delta, an m-gamma_t-critical graph exists if and only if Delta \ge 2 \lfloor \frac{m-1}{2}\rfloor; for m=4 or odd m \ge 3 and for odd Delta, if Delta \ge 2\lfloor \frac{m-1}{2}\rfloor +7, then m-gamma_t-critical graphs exist, if Delta < 2\lfloor \frac{m-1}{2}\rfloor, then m-gamma_t-critical graphs do not exist. The only remaining open cases are Delta = 2\lfloor \frac{m-1}{2}\rfloor +k, k=1, 3, 5. Second, we study these remaining open cases when m=4 or odd m \ge 9. As the previously known result for m = 3, we also show that for Delta(G)= 3, 5, 7, there is no 4-gamma_t-critical graph of order Delta(G)+4. On the contrary, it is shown that for odd m \ge 9 there exists an m-gamma_t-critical graph for all Delta \ge m-1.

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