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COMBINATORICS
2000
89views more  COMBINATORICS 2000»
15 years 5 months ago
A Note on the Non-Colorability Threshold of a Random Graph
In this paper we consider the problem of establishing a value r0 such that almost all random graphs with n vertices and rn edges, r > r0, are asymptotically not 3-colorable. In...
Alexis C. Kaporis, Lefteris M. Kirousis, Yannis C....
COMBINATORICS
2000
82views more  COMBINATORICS 2000»
15 years 5 months ago
The Strongly Regular (40, 12, 2, 4) Graphs
In a previous paper it was established that there are at least 27 non-isomorphic strongly regular (40, 12, 2, 4) graphs. Using a different and more efficient method we have re-inv...
Edward Spence
150
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COMBINATORICS
2000
89views more  COMBINATORICS 2000»
15 years 5 months ago
Large Dihedral Symmetry of the Set of Alternating Sign Matrices
We prove a conjecture of Cohn and Propp, which refines a conjecture of Bosley and Fidkowski about the symmetry of the set of alternating sign matrices (ASMs). We examine data aris...
Benjamin Wieland
COMBINATORICS
2002
65views more  COMBINATORICS 2002»
15 years 5 months ago
Sorting with a Forklift
A fork stack is a generalised stack which allows pushes and pops of several items at a time. We consider the problem of determining which input streams can be sorted using a singl...
Michael H. Albert, Mike D. Atkinson
COMBINATORICS
2002
88views more  COMBINATORICS 2002»
15 years 5 months ago
Graph Color Extensions: When Hadwiger's Conjecture and Embeddings Help
Suppose G is r-colorable and P V (G) is such that the components of G[P] are far apart. We show that any (r + s)-coloring of G[P] in which each component is s-colored extends to ...
Michael O. Albertson, Joan P. Hutchinson