Graph Theory » Basic G.T. » Matchings

Exponentially many perfect matchings in cubic graphs ★★★

Author(s): Lovasz; Plummer

Conjecture   There exists a fixed constant $ c $ so that every $ n $-vertex cubic graph without a cut-edge has at least $ e^{cn} $ perfect matchings.

Keywords: cubic; perfect matching

Posted by mdevos
updated December 15th, 2010
2 comments
Graph Theory » Infinite Graphs

Characterizing (aleph_0,aleph_1)-graphs ★★★

Author(s): Diestel; Leader

Call a graph an $ (\aleph_0,\aleph_1) $-graph if it has a bipartition $ (A,B) $ so that every vertex in $ A $ has degree $ \aleph_0 $ and every vertex in $ B $ has degree $ \aleph_1 $.

Problem   Characterize the $ (\aleph_0,\aleph_1) $-graphs.

Keywords: binary tree; infinite graph; normal spanning tree; set theory

Posted by mdevos
updated November 24th, 2011
2 comments
Graph Theory » Coloring

4-regular 4-chromatic graphs of high girth ★★

Author(s): Grunbaum

Problem   Do there exist 4-regular 4-chromatic graphs of arbitrarily high girth?

Keywords: coloring; girth

Posted by mdevos
updated January 29th, 2012
2 comments