错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

List-Avoiding Orientations

  • Peter Bradshaw,
  • Yaobin Chen,
  • Hao Ma,
  • Bojan Mohar,
  • Hehui Wu

摘要

Given a graph G with a set F(v) of forbidden values at each \(v \in V(G)\) v V ( G ) , an F-avoiding orientation of G is an orientation in which \(\deg ^+(v) \not \in F(v)\) deg + ( v ) F ( v ) for each vertex v. Akbari, Dalirrooyfard, Ehsani, Ozeki, and Sherkati conjectured that if \(|F(v)| < \frac{1}{2} \deg (v)\) | F ( v ) | < 1 2 deg ( v ) for each \(v \in V(G)\) v V ( G ) , then G has an F-avoiding orientation, and they showed that this statement is true when \(\frac{1}{2}\) 1 2 is replaced by \(\frac{1}{4}\) 1 4 . In this paper, we take a step toward this conjecture by proving that if \(|F(v)| < \lfloor \frac{1}{3} \deg (v) \rfloor \) | F ( v ) | < 1 3 deg ( v ) for each vertex v, then G has an F-avoiding orientation. Furthermore, we show that if the maximum degree of G is subexponential in terms of the minimum degree, then this coefficient of \(\frac{1}{3}\) 1 3 can be increased to \(\sqrt{2} - 1 - o(1) \approx 0.414\) 2 - 1 - o ( 1 ) 0.414 . Our main tool is a new sufficient condition for the existence of an F-avoiding orientation based on the Combinatorial Nullstellensatz of Alon and Tarsi.