• Publications
  • Influence
On the complexity of H-coloring
The natural conjecture, formulated in several sources, asserts that the H-coloring problem is NP-complete for any non-bipartite graph H, and a proof of this conjecture is given. Expand
Graphs and homomorphisms
  • P. Hell, J. Nesetril
  • Computer Science, Mathematics
  • Oxford lecture series in mathematics and its…
  • 2004
This chapter discusses the structure of Composition, the partial order of Graphs and Homomorphisms, and testing for the Existence of Homomorphism. Expand
Sparsity - Graphs, Structures, and Algorithms
This is the first book devoted to the systematic study of sparse graphs and sparse finite structures and the authors devised an unifying classification of general classes of structures that is very robust and has many remarkable properties. Expand
Tree-depth, subgraph coloring and homomorphism bounds
The notions tree-depth and upper chromatic number of a graph are defined and it is shown that the upper chromatics number coincides with the maximal function which can be locally demanded in a bounded coloring of any proper minor closed class of graphs. Expand
Grad and classes with bounded expansion I. Decompositions
For classes of graphs with bounded expansion with a new invariant, the greatest reduced average density of G with rankr, @?"r(G) is introduced, it is proved the existence of several partition results such as theexistence of low tree-width and lowTree-depth colorings. Expand
Homomorphism-Homogeneous Relational Structures
  • P. Cameron, J. Nesetril
  • Computer Science, Mathematics
  • Combinatorics, Probability and Computing
  • 1 January 2006
The main results are partial characterizations of countable graphs and posets with this property; an analogue of Fraïssé's theorem; and representations of monoids as endomorphism monoids of such structures. Expand
On nowhere dense graphs
The nowhere dense versus somewhere dense dichotomy is expressed in terms of edge densities as a trichotomy theorem and has a number of applications to mathematical logic, complexity of algorithms, and combinatorics. Expand
The core of a graph
It is found that the core of a finite graph is unique (up to isomorphism) and is also its smallest retract, and some homomorphism properties of cores are investigated, concluding that it is NP-complete to decide whether a graph is its own core. Expand
The Ramsey property for graphs with forbidden complete subgraphs
Abstract The following theorem is proved: Let G be a finite graph with cl( G ) = m , where cl( G ) is the maximum size of a clique in G . Then for any integer r ≥ 1, there is a finite graph H , alsoExpand