It is proved that a planar graph with maximum degree โ โฅ 11 has total (vertex-edge) chromatic number โ + 1.
(n,e)-Graphs with maximum sum of squares of degrees*
โ Scribed by Peled, Uri N.; Petreschi, Rossella; Sterbini, Andrea
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 308 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
โฆ Synopsis
Among all simple graphs on n vertices and e edges, which ones have the largest sum of squares of the vertex degrees? It is easy to see that they must be threshold graphs, but not every threshold graph is optimal in this sense. Boesch et al. [Boesch et al., Tech Rep, Stevens Inst Tech, Hoboken NJ, 1990] showed that for given n and e there exists exactly one graph of the form G 1 (p, q, r) = K p + (S q โช K 1,r ) and exactly one G 2 (p, q, r) = S p โช (K q + K 1,r ) and that one of them is optimal, where K and S indicate complete and edgeless graphs, K 1,r indicates a star on r + 1 vertices, โช indicates disjoint union, and + indicates complete disjoint join. We specify a general threshold graph in the form G * 1 (a, b, c, d, . . .
๐ SIMILAR VOLUMES
d 2,n 2 ) is a bipartite graphical sequence, if there is a bipartite graph G with degrees {D 1 , D 2 } (i.e., G has two independent vertex sets In other words, {D 1 , D 2 } is a bipartite graphical sequence if and only if there is an n 1 1 n 2 matrix of 0's and 1's having d 1j 1 1's in row j 1 and