设 (是≥2)为n阶的染色数为k的连通图的集合.本文确定了 中具有极大无符号Laplace谱半径的图,即k=2时为完全二部图,k≥3时为Turan图.本文也讨论了 中的具有极小无符号Laplace谱半径的图,对k≤3的情形给出了此类图的刻画.
Let (k ≥ 2) be the set of all connected graphs of order n with chromatic number k. We determine the graphs with maximal signless Laplacian spectral radius among all graphs in , namely complete bipartite graphs for k = 2 and Turin graph for k ≥ 3. We also consider the graphs with minimal signless Laplacian spectral radius in , and characterized such graphs for k ≤3.