Prof Pavol Hell Publications

dichotomylist homomorphismsdigraphs

latintheoretical informaticsOaxacaspringer faithful representationsgraphsextended grid

retractionspseudoforests

adaptable chromatic numbergraph products

linear-time certifying algorithmsnear-graphical sequences

canadiancomputational geometry vancouvercolumbiageneralizationsinterval graphs

adjusted interval digraphs

extension problemsdegree bounds

cycle transversalsbounded degree graphs

dualitymin-max orderingsdichotomymin cost homomorphisms

adaptable chromatic numbergraphs

colouring constraint satisfactioncomplexity

latintheoretical informaticsbziosspringerinjective colouringschordal graphs

polaritychordal graphs

dichotomyminimum cost graph homomorphisms

latintheoretical informaticsbziosspringer minimum cost homomorphismsreflexive digraphs

oriented star packings

realizationspoint determining graphsobstructionshomomorphisms

brooks-type theoremspair-list coloringslist homomorphisms

near-unanimity functionsvarietiesreflexive graphs

For digraphs $G$ and $H$, a homomorphism of $G$ to $H$ is a mapping $f:\ V(G)\dom V(H)$ such that $uv\in A(G)$ implies $f(u)f(v)\in A(H)$. If moreover each vertex $u \in V(G)$ is associated with costs...

minimum cost homomorphismsreflexive digraphs

structurebi-arc trees

list homomorphismsgraphsbounded degrees

matrix partitionsfinitelyobstructions

constraint satisfaction problems

digraph matrix partitionstrigraph homomorphisms

k-piece packing problem

independent packingsstructured graphs

minimum cost homomorphismsproper interval graphsbigraphs

matrix partitionsperfect graphs

packing r-cliquesweighted chordal graphs

generalizationtheoremlekkerkerkerboland

acm-siamdiscrete algorithms soda vancouvercolumbiasiamalgorithmsgeneral list matrix partitions

list matrix partitionschordal graphs

interval bigraphscircular arc graphs

partitioning chordal graphsindependent setscliques

polychromatic cliques

List matrix partitions are restricted binary list constraint satisfaction problems which generalize list homomorphisms and many graph partition problems arising, e.g., in the study of perfect graphs. ...

certifying lexbfs recognition algorithmsproper interval graphsproper interval bigraphs

List matrix partitions are restricted binary list constraint satisfaction problems which generalize list homomorphisms and many graph partition problems arising, e.g., in the study of perfect graphs. ...

latintheoretical informaticsbuenos airesspringer list partitionschordal graphs

spanning spiderslight-splitting switches

The sub-Ramsey number sr(Kn ; k) is the smallest integer m such that in any edge-colouring of Km which uses every colour at most k times some subgraph Kn has all edges of dierent colours. It was known...

broadcastinggeneralized chordal rings

acyclic homomorphismscircular coloringsdigraphs

antidirected hamiltonian pathsspecified verticestournament

homomorphismspowersdigraphs

automata languagesprogrammingicalp malagaspringer spanning treesbounded numberbranch vertices

fully dynamic algorithmrecognizingrepresenting proper interval graphs

nice graphs

We discuss a number of variants of the homomorphism problem, where input graphs G are to be mapped homomorphically to a xed target graph H. We set up a structure unifying the work on nding graph homom...

generalized split graphs

high-girth graphs avoidingminornearly bipartite

graph packings

homomorphismsedge-coloured cycles

complexityh-colouringbounded degree graphs

Let H be a fixed graph. We show that any H-minor free graph of high enough girth has a circular-chromatic number arbitrarily close to two. Equivalently, such graphs have homomorphisms into a large odd...

algorithmsesapraguespringerfully dynamic algorithmrecognizingrepresenting proper interval graphs

We discuss the existence of homomorphisms of arbitrary digraphs to a xed oriented cycle C. Our main result asserts that if the cycle C is unbalanced then a digraph G is homomorphic to C if and only if...

Let T be a symmetric directed tree, i.e., an undirected tree with each edge viewed as two opposite arcs. We prove that the minimum number of colours needed to colour the set of all directed paths in T...

We introduce a parametrized family of graph problems that includes several well-known graph partition problems as special cases. We develop tools which allow us to classify the complexity of many prob...

stoc complexitygraph partition problemsSTOC

list homomorphismscircular arc graphs

Let G be a fixed collection of digraphs. Given a digraph H, a G- packing of H is a collection of vertex disjoint subgraphs of H, each isomorphic to a member of G. A G-packing, P, is maximum if the num...

. We outline constructions of packet radio networks (with time division multiplexing) that achieve much better parameters than those previously proposed. Given the desired diameter and number of slots...

constructionslarge planar networksgiven degreediameter

complexitycoloring areflexive h-ary relationsgiven permutation group

list homomorphismsreflexive graphs

optimal wavelength-routed multicasting

This paper surveys the theoretical results obtained for wavelength--routing all--optical networks, presents some new results and proposes several open problems. In all--optical networks the vast bandw...

: Motivated by wavelength division multiplexing in all-optical networks, we consider the problem of finding a set of paths from a fixed source to a multiset of destinations, which can be coloured by t...

complexityrestricted graph homomorphisms

. Let T be a symmetric directed tree, i.e., an undirected tree with each edge viewed as two opposite arcs. We prove that the minimum number of colours needed to colour the set of all directed paths in...

automata languagesprogrammingicalp bolognaspringer colouring pathsdirected symmetric treesapplicationswdm routing

roundingsymmetric matricesundirected graphs

complexitytree homomorphisms

linear-time representation algorithmsproper circular-arc graphsproper interval graphs

linear algorithmmaximum weight cliquespropercircular arc graphs

existencehomomorphismsoriented cycles

large planar graphsgiven diametermaximum degree

combinatoricssciencefranco-japanesefranco-chinesebrestselected papers springer findingantidirected hamiltonian path startingforward arcgiven vertextournamentselected papers

hereditarily hard h-colouring problems

multiplicativityoriented cycles

packing problemsedge-colored graphs

independence ratiosgraph powers

homomorphismsoriented paths

chordal proper circular arc graphs

homomorphismsoriented cycles

algorithmsdegree constrained graph factorsminimum deficiency

largest planar graphsdiameterfixed maximum degree

biographymartin farber

fast algorithmsfinding hamiltonian pathscyclesin-tournament digraphs

universalitya-mote graphs

absolute reflexive retractsabsolute bipartite retracts

achromatic numbersgraph operations

coregraph

broadcastingbounded degree graphs

sparse broadcast graphs

constructionlarge packet radio networks

integer programmingcombinatorial optimizationpittsburgh pacarnegie mellonrepresentationproper circular arc graphs

complexitycolouringsuperdigraphsbipartite graphs

complexityh-coloring

algorithmssigal tokyospringer local tournamentsproper circular arc gaphs

effectcyclescomplexitycolouringsdirected graphs

simple existence criteriong lt f)factors

broadcastingdimension

restricted two-factors

complexitycolouringsemicomplete digraphs

multiplicative graphsproduct conjecture

concerningachromatic numbergraphs

packingscliquesfinite familiesgraphs

complexityfinding generalized pathstournaments

complexitygeneral graph factor problems

generalized matching problems

parallel sortingconstant timecomparisons

recordtheorycomputingdiego californiacompletenessgeneralized matching problem