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The Ramsey Number for Tree Versus Wheel with Odd Order
Bulletin of the Malaysian Mathematical Sciences Society ( IF 1.2 ) Pub Date : 2021-01-05 , DOI: 10.1007/s40840-020-01055-x
Yusuf Hafidh , Edy Tri Baskoro

Chen et al. (Appl Math Lett 17:281–285, 2004) conjectured that for even m, \(R(T_n,W_m)=2n-1\) if the maximum degree \(\varDelta (T_n)\) is small. However, they did not state how small it is. Related to this conjecture, it is also interesting to know which tree \(T_n\) causes the Ramsey number \(R(T_n,W_m)\) to be greater than \(2n-1\) whenever m is even. In this paper, we determine the Ramsey number \(R(T_n,W_8)\) for all trees \(T_n\) with \(\varDelta (T_n) \ge n-3\). For most cases of these trees, \(R(T_n,W_8) > 2n-1\). Furthermore, we also prove that for certain values of n, the Ramsey number \(R(T_n,W_m)\) is greater than \(2n-1\) if \(\varDelta (T_n) \ge n-3\) and m is even. Finally, we refine the above conjecture by giving an upper bound on the maximum degree of the tree \(T_n\).



中文翻译:

树对轮子的奇数阶Ramsey数

Chen等。(Appl Math Lett 17:281–285,2004)推测,如果最大度数\(\ varDelta(T_n)\)小,则对于偶数m\(R(T_n,W_m)= 2n-1 \)。但是,他们没有说明它有多小。与此猜想相关,每当m为偶数时,知道哪棵树\(T_n \)导致拉姆齐数\(R(T_n,W_m)\)大于\(2n-1 \)也很有趣。在本文中,我们确定具有\(\ varDelta(T_n)\ ge n-3 \)的所有树木\(T_n \)的Ramsey数\ {R(T_n,W_8)\)。对于这些树的大多数情况,\(R(T_n,W_8)> 2n-1 \)。此外,我们还证明,对于n的某些值,如果\(\ varDelta(T_n)\ ge n-3 \),则拉姆西数\(R(T_n,W_m)\)大于\(2n-1 \)。是偶数。最后,我们通过给出树的最大程度\(T_n \)的上限来完善上述猜想。

更新日期:2021-01-06
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