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JCT
2007
140views more  JCT 2007»
13 years 11 months ago
Homomorphisms and edge-colourings of planar graphs
We conjecture that every planar graph of odd-girth 2k + 1 admits a homomorphism to Cayley graph C(Z2k+1 2 , S2k+1), with S2k+1 being the set of (2k + 1)vectors with exactly two co...
Reza Naserasr
CORR
2007
Springer
119views Education» more  CORR 2007»
13 years 11 months ago
Minimum Cost Homomorphisms to Locally Semicomplete and Quasi-Transitive Digraphs
For digraphs G and H, a homomorphism of G to H is a mapping f : V (G)→V (H) such that uv ∈ A(G) implies f(u)f(v) ∈ A(H). If, moreover, each vertex u ∈ V (G) is associated ...
Arvind Gupta, Gregory Gutin, Mehdi Karimi, Eun Jun...
IPL
2006
153views more  IPL 2006»
13 years 11 months ago
Oriented vertex and arc colorings of outerplanar graphs
A homomorphism from an oriented graph G to an oriented graph H is an arc-preserving mapping from V (G) to V (H), that is (x)(y) is an arc in H whenever xy is an arc in G. The orie...
Alexandre Pinlou, Eric Sopena
IPL
2008
169views more  IPL 2008»
13 years 11 months ago
Oriented colorings of partial 2-trees
A homomorphism from an oriented graph G to an oriented graph H is an arc-preserving mapping f from V(G) to V(H), that is f(x)f(y) is an arc in H whenever xy is an arc in G. The or...
Pascal Ochem, Alexandre Pinlou
CORR
2006
Springer
128views Education» more  CORR 2006»
13 years 11 months ago
Minimum Cost Homomorphisms to Semicomplete Bipartite Digraphs
For digraphs D and H, a mapping f : V (D)V (H) is a homomorphism of D to H if uv A(D) implies f(u)f(v) A(H). If, moreover, each vertex u V (D) is associated with costs ci(u), i...
Gregory Gutin, Arash Rafiey, Anders Yeo
COMBINATORICS
2006
183views more  COMBINATORICS 2006»
13 years 11 months ago
On Oriented Arc-Coloring of Subcubic Graphs
A homomorphism from an oriented graph G to an oriented graph H is a mapping from the set of vertices of G to the set of vertices of H such that -----(u)(v) is an arc in H whenever...
Alexandre Pinlou
DAM
2008
129views more  DAM 2008»
13 years 11 months ago
Minimum cost homomorphisms to semicomplete multipartite digraphs
For digraphs D and H, a mapping f : V (D)V (H) is a homomorphism of D to H if uv A(D) implies f(u)f(v) A(H). For a fixed directed or undirected graph H and an input graph D, the...
Gregory Gutin, Arash Rafiey, Anders Yeo
ISAAC
2007
Springer
146views Algorithms» more  ISAAC 2007»
14 years 5 months ago
Bounded Tree-Width and CSP-Related Problems
We study the complexity of structurally restricted homomorphism and constraint satisfaction problems. For every class of relational structures C, let LHOM(C, _) be the problem of d...
Tommy Färnqvist, Peter Jonsson
AAIM
2008
Springer
120views Algorithms» more  AAIM 2008»
14 years 5 months ago
Minimum Cost Homomorphism Dichotomy for Oriented Cycles
For digraphs D and H, a mapping f : V (D)→V (H) is a homomorphism of D to H if uv ∈ A(D) implies f(u)f(v) ∈ A(H). If, moreover, each vertex u ∈ V (D) is associated with co...
Gregory Gutin, Arash Rafiey, Anders Yeo
CSR
2009
Springer
14 years 6 months ago
New Plain-Exponential Time Classes for Graph Homomorphism
A homomorphism from a graph G to a graph H (in this paper, both simple, undirected graphs) is a mapping f : V (G) → V (H) such that if uv ∈ E(G) then f(u)f(v) ∈ E(H). The pro...
Magnus Wahlström