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JCT
2010
95views more  JCT 2010»
14 years 8 months ago
Oriented diameter of graphs with diameter 3
In 1978, Chv´atal and Thomassen proved that every 2-edge-connected graph with diameter 2 has an orientation with diameter at most 6. They also gave general bounds on the smallest...
Peter K. Kwok, Qi Liu, Douglas B. West
JCT
2010
91views more  JCT 2010»
14 years 8 months ago
Lattice path matroids: The excluded minors
A lattice path matroid is a transversal matroid for which some antichain of intervals in some linear order on the ground set is a presentation. We characterize the minor-closed cla...
Joseph E. Bonin
JCT
2010
70views more  JCT 2010»
14 years 8 months ago
Graphs with bounded tree-width and large odd-girth are almost bipartite
We prove that for every k and every ε > 0, there exists g such that every graph with tree-width at most k and odd-girth at least g has circular chromatic number at most 2 + ε...
Alexandr V. Kostochka, Daniel Král', Jean-S...
JCT
2010
80views more  JCT 2010»
14 years 8 months ago
Shadows and intersections in vector spaces
We prove a vector space analog of a version of the Kruskal-Katona theorem due to Lov´asz. We apply this result to extend Frankl’s theorem on r-wise intersecting families to vec...
Ameera Chowdhury, Balázs Patkós
JCT
2010
93views more  JCT 2010»
14 years 8 months ago
Ramanujan's lost notebook: Combinatorial proofs of identities associated with Heine's transformation or partial theta functions
Combinatorial proofs are given for certain entries in Ramanujan’s lost notebook. Bijections of Sylvester, Franklin, Wright, and Yee are employed. A new bijection, involving the n...
Bruce C. Berndt, Byungchan Kim, Ae Ja Yee