Professor Daniel Paulusma's Outputs (314)

Surjective H-Colouring: new hardness results (2017)
Presentation / Conference Contribution
Golovach, P. A., Johnson, M., Martin, M., Paulusma, D., & Stewart, A. (2017, June). Surjective H-Colouring: new hardness results. Presented at Computability in Europe (CiE 2017)., Turku, Finland

A homomorphism from a graph G to a graph H is a vertex mapping f from the vertex set of G to the vertex set of H such that there is an edge between vertices f(u) and f(v) of H whenever there is an edge between vertices u and v of G. The H-Colouring p... Read More about Surjective H-Colouring: new hardness results.

Blocking independent sets for H-free graphs via edge contractions and vertex deletions (2017)
Presentation / Conference Contribution
Paulusma, D., Picouleau, C., & Ries, B. (2017, April). Blocking independent sets for H-free graphs via edge contractions and vertex deletions. Presented at Theory and applications of models of computation, 14th Annual Conference, TAMC 2017, Bern, Switzerland

Let d and k be two given integers, and let G be a graph. Can we reduce the independence number of G by at least d via at most k graph operations from some fixed set S? This problem belongs to a class of so-called blocker problems. It is known to be c... Read More about Blocking independent sets for H-free graphs via edge contractions and vertex deletions.

Bounding the Clique-Width of H-free Chordal Graphs (2017)
Journal Article
Brandstädt, A., Dabrowski, K., Huang, S., & Paulusma, D. (2017). Bounding the Clique-Width of H-free Chordal Graphs. Journal of Graph Theory, 86(1), 42-77. https://doi.org/10.1002/jgt.22111

A graph is H-free if it has no induced subgraph isomorphic to H. Brandstädt, Engelfriet, Le, and Lozin proved that the class of chordal graphs with independence number at most 3 has unbounded clique-width. Brandstädt, Le, and Mosca erroneously claime... Read More about Bounding the Clique-Width of H-free Chordal Graphs.

The Stable Fixtures Problem with Payments (2017)
Journal Article
Biró, P., Kern, W., Paulusma, D., & Wojuteczky, P. (2018). The Stable Fixtures Problem with Payments. Games and Economic Behavior, 108, 245-268. https://doi.org/10.1016/j.geb.2017.02.002

We consider multiple partners matching games (G,b,w), where G is a graph with an integer vertex capacity function b and an edge weighting w. If G is bipartite, these games are called multiple partners assignment games. We give a polynomial-time algor... Read More about The Stable Fixtures Problem with Payments.

Independent Feedback Vertex Set for P5-free Graphs (2017)
Presentation / Conference Contribution
Bonamy, M., Dabrowski, K. K., Feghali, C., Johnson, M., & Paulusma, D. (2017, December). Independent Feedback Vertex Set for P5-free Graphs. Presented at ISAAC 2017

The NP-complete problem Feedback Vertex Set is to decide if it is possible, for a given integer k ≥ 0, to delete at most k vertices from a given graph so that what remains is a forest. The variant in which the deleted vertices must form an independen... Read More about Independent Feedback Vertex Set for P5-free Graphs.

Editing to a Planar Graph of Given Degrees (2016)
Journal Article
Dabrowski, K., Golovach, P., van 't Hof, P., Paulusma, D., & Thilikos, D. (2016). Editing to a Planar Graph of Given Degrees. Journal of Computer and System Sciences, 85, 168-182. https://doi.org/10.1016/j.jcss.2016.11.009

We consider the following graph modification problem. Let the input consist of a graph G=(V,E), a weight function w:V∪E→N, a cost function c:V∪E→N0 and a degree function δ:V→N0, together with three integers kv,ke and C . The question is whether we ca... Read More about Editing to a Planar Graph of Given Degrees.

Squares of low clique number (2016)
Presentation / Conference Contribution
Golovach, P., Kratsch, D., Paulusma, D., & Stewart, A. Squares of low clique number. Presented at 14th Cologne-Twente Workshop on Graphs and Combinatorial Optimization (CTW16), Gargnano, Italy

The Square Root problem is that of deciding whether a given graph admits a square root. This problem is only known to be NP-complete for chordal graphs and polynomial-time solvable for non-trivial minor-closed graph classes and a very limited number... Read More about Squares of low clique number.

The price of connectivity for feedback vertex set (2016)
Journal Article
Belmonte, R., van ’t Hof, P., Kamiński, M., & Paulusma, D. (2017). The price of connectivity for feedback vertex set. Discrete Applied Mathematics, 217(Part B), 132-143. https://doi.org/10.1016/j.dam.2016.08.011

Let View the MathML source and View the MathML source denote the cardinalities of a minimum feedback vertex set and a minimum connected feedback vertex set of a graph G, respectively. The price of connectivity for feedback vertex set (poc-fvs) for a... Read More about The price of connectivity for feedback vertex set.

Reducing the clique and chromatic number via edge contractions and vertex deletions (2016)
Presentation / Conference Contribution
Paulusma, D., Picouleau, C., & Ries, B. (2016, May). Reducing the clique and chromatic number via edge contractions and vertex deletions. Presented at 4th International Symposium on Combinatorial Optimization (ISCO 2016), Vietri sul Mare, Italy

We consider the following problem: can a certain graph parameter of some given graph G be reduced by at least d, for some integer d, via at most k graph operations from some specified set S, for some given integer k? As graph parameters we take the c... Read More about Reducing the clique and chromatic number via edge contractions and vertex deletions.

Finding cactus roots in polynomial time (2016)
Presentation / Conference Contribution
Golovach, P. A., Kratsch, D., Paulusma, D., & Stewart, A. (2016, August). Finding cactus roots in polynomial time. Presented at 27th International Workshop on Combinatorial Algorithms (IWOCA 2016)., Helsinki, Finland

A cactus is a connected graph in which each edge belongs to at most one cycle. A graph H is a cactus root of a graph G if H is a cactus and G can be obtained from H by adding an edge between any two vertices in H that are of distance 2 in H. We show... Read More about Finding cactus roots in polynomial time.

Well-quasi-ordering versus clique-width: new results on bigenic classes (2016)
Presentation / Conference Contribution
Dabrowski, K. K., Lozin, V. V., & Paulusma, D. (2016, August). Well-quasi-ordering versus clique-width: new results on bigenic classes. Presented at 27th International Workshop on Combinatorial Algorithms (IWOCA 2016)., Helsinki, Finland

Daligault, Rao and Thomassé conjectured that if a hereditary class of graphs is well-quasi-ordered by the induced subgraph relation then it has bounded clique-width. Lozin, Razgon and Zamaraev recently showed that this conjecture is not true for infi... Read More about Well-quasi-ordering versus clique-width: new results on bigenic classes.

Minimal Disconnected Cuts in Planar Graphs (2016)
Journal Article
Kamiński, M., Paulusma, D., Stewart, A., & Thilikos, D. (2016). Minimal Disconnected Cuts in Planar Graphs. Networks, 68(4), 250-259. https://doi.org/10.1002/net.21696

The problem of finding a disconnected cut in a graph is NP-hard in general but polynomial-time solvable on planar graphs. The problem of finding a minimal disconnected cut is also NP-hard but its computational complexity was not known for planar grap... Read More about Minimal Disconnected Cuts in Planar Graphs.

Open problems on graph coloring for special graph classes (2016)
Presentation / Conference Contribution
Paulusma, D. (2015, June). Open problems on graph coloring for special graph classes. Presented at 41st International Workshop on Graph-Theoretic Concepts in Computer Science (WG 2015), Munich, Germany

For a given graph G and integer k, the Coloring problem is that of testing whether G has a k-coloring, that is, whether there exists a vertex mapping c:V→{1,2,…}c:V→{1,2,…} such that c(u)≠c(v)c(u)≠c(v) for every edge uv∈Euv∈E. We survey known results... Read More about Open problems on graph coloring for special graph classes.

The stable fixtures problem with payments (2016)
Presentation / Conference Contribution
Biró, P., Kern, W., Paulusma, D., & Wojuteczky, P. (2015, June). The stable fixtures problem with payments. Presented at 41 International Workshop on Graph-Theoretic Concepts in Computer Science (WG 2015), Munich, Germany

We generalize two well-known game-theoretic models by introducing multiple partners matching games, defined by a graph G=(N,E)G=(N,E), with an integer vertex capacity function b and an edge weighting w. The set N consists of a number of players that... Read More about The stable fixtures problem with payments.

Using contracted solution graphs for solving reconfiguration problems (2016)
Presentation / Conference Contribution
Bonsma, P., & Paulusma, D. (2016, August). Using contracted solution graphs for solving reconfiguration problems. Presented at 41st International Symposium on Mathematical Foundations of Computer Science (MFCS 2016), Krakow, Poland

We introduce a dynamic programming method for solving reconfiguration problems, based on contracted solution graphs, which are obtained from solution graphs by performing an appropriate series of edge contractions that decrease the graph size without... Read More about Using contracted solution graphs for solving reconfiguration problems.

Kempe equivalence of colourings of cubic graphs (2016)
Journal Article
Feghali, C., Johnson, M., & Paulusma, D. (2017). Kempe equivalence of colourings of cubic graphs. European Journal of Combinatorics, 59, 1-10. https://doi.org/10.1016/j.ejc.2016.06.008

Given a graph G=(V,E) and a proper vertex colouring of G, a Kempe chain is a subset of V that induces a maximal connected subgraph of G in which every vertex has one of two colours. To make a Kempe change is to obtain one colouring from another by ex... Read More about Kempe equivalence of colourings of cubic graphs.

Bounding clique-width via perfect graphs (2016)
Journal Article
Dabrowski, K., Huang, S., & Paulusma, D. (2019). Bounding clique-width via perfect graphs. Journal of Computer and System Sciences, 104, 202-215. https://doi.org/10.1016/j.jcss.2016.06.007

We continue the study into the clique-width of graph classes defined by two forbidden induced graphs. We present three new classes of bounded clique-width and one of unbounded clique-width. The four new graph classes have in common that one of their... Read More about Bounding clique-width via perfect graphs.

The price of connectivity for cycle transversals (2016)
Journal Article
Hartinger, T., Johnson, M., Milanič, M., & Paulusma, D. (2016). The price of connectivity for cycle transversals. European Journal of Combinatorics, 58, 203-224. https://doi.org/10.1016/j.ejc.2016.06.003

For a family of graphs F, an F-transversal of a graph G is a subset S⊆V(G) that intersects every subset of V(G) that induces a subgraph isomorphic to a graph in F. Let tF(G) be the minimum size of an F-transversal of G, and View the MathML source be... Read More about The price of connectivity for cycle transversals.

A linear kernel for finding square roots of almost planar graphs (2016)
Presentation / Conference Contribution
Golovach, P., Kratsch, D., Paulusma, D., & Stewart, A. (2016, June). A linear kernel for finding square roots of almost planar graphs. Presented at 15th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2016), Reykjavik, Iceland

A graph H is a square root of a graph G if G can be obtained from H by the addition of edges between any two vertices in H that are of distance 2 of each other. The Square Root problem is that of deciding whether a given graph admits a square root. W... Read More about A linear kernel for finding square roots of almost planar graphs.

Colouring diamond-free graphs (2016)
Presentation / Conference Contribution
Dabrowski, K. K., Dross, F., & Paulusma, D. (2016, June). Colouring diamond-free graphs. Presented at 15th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2016), Reykjavik, Iceland

The Colouring problem is that of deciding, given a graph G and an integer k, whether G admits a (proper) k-colouring. For all graphs H up to five vertices, we classify the computational complexity of Colouring for (diamond,H)-free graphs. Our proof i... Read More about Colouring diamond-free graphs.