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JCT
2007
140views more  JCT 2007»
8 years 8 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»
8 years 8 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»
8 years 8 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»
8 years 8 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»
8 years 8 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»
8 years 8 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»
8 years 8 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»
9 years 2 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»
9 years 2 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
9 years 2 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
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