混合超图是含有两类超边的超图,一类称为G-超边,一类称为D-超边,它们的区别主要体现在染色要求上.混合超图的染色,要求每一G-超边至少有两个点染相同的颜色,而每一D-超边至少有两个点染不同的颜色.所用的最大颜色数称为对应混合超图的上色数,所用的最小颜色数称为对应混合超图的下色数.上、下色数与边数有密切关系.作者在文献[2]中证明了具有最小上色数的3一致G-超图边数的一个下界为[n(n-2)/3],其中n为对应混合超图的顶点数.该文证明当n=2^k+1时,该下界是可以达到的.
The upper chromatic number X^-(H) of a C-hypergraph H= (X, C) is the maximum number of colors that can be assigned to the vertices of H in such a way that each C ∈ C contains a monochromatic pair of vertices, This paper discusses the relationship between the lower bound of the upper chromatic numbers and the lower bound of the sizes of C-edges of a C- hypergraph and proves that the lower bound of the size of C-edges of 3-uniform C-hypergraphs given in [2] is achievable when n = 2^k + 1.