We prove several tight lower bounds in terms of the order and the average degree for the independence number of graphs that are connected and/or satisfy some odd girth condition. Our main result is the extension of a lower bound for the independence number of triangle-free graphs of maximum degree a
Average degree and contractibility
β Scribed by Matthias Kriesell
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 197 KB
- Volume
- 51
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
β¦ Synopsis
It is proved that for every number k there exists a number f (k) such that every finite k-connected graph of average degree exceeding f (k) contains an edge whose contraction yields again a k-connected graph. For the proof, tree orders on certain sets of smallest separating sets of the graph in question are constructed. This leads to new canonical tree decompositions as well.
π SIMILAR VOLUMES
The average distance Β΅(G) of a connected graph G of order n is the average of the distances between all pairs of vertices of G, i.e., Β΅(G) = ( n 2 ) -1 {x,y}βV (G) d G (x, y), where V (G) denotes the vertex set of G and d G (x, y) is the distance between x and y. We prove that every connected graph
## Abstract Improper choosability of planar graphs has been widely studied. In particular, Ε krekovski investigated the smallest integer __g__~k~ such that every planar graph of girth at least __g__~k~ is __k__βimproper 2βchoosable. He proved [9] that 6ββ€β__g__~1~ β€β9; 5ββ€β __g__~2~ββ€β7; 5ββ€β__g__~3
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