15 research outputs found
On local structures of cubicity 2 graphs
A 2-stab unit interval graph (2SUIG) is an axes-parallel unit square
intersection graph where the unit squares intersect either of the two fixed
lines parallel to the -axis, distance ()
apart. This family of graphs allow us to study local structures of unit square
intersection graphs, that is, graphs with cubicity 2. The complexity of
determining whether a tree has cubicity 2 is unknown while the graph
recognition problem for unit square intersection graph is known to be NP-hard.
We present a polynomial time algorithm for recognizing trees that admit a 2SUIG
representation
Deciding the Bell Number for Hereditary Graph Properties
The paper [J. Balogh, B. Bollobás, D. Weinreich, J. Combin. Theory Ser. B, 95 (2005), pp. 29--48] identifies a jump in the speed of hereditary graph properties to the Bell number and provides a partial characterization of the family of minimal classes whose speed is at least . In the present paper, we give a complete characterization of this family. Since this family is infinite, the decidability of the problem of determining if the speed of a hereditary property is above or below the Bell number is questionable. We answer this question positively by showing that there exists an algorithm which, given a finite set of graphs, decides whether the speed of the class of graphs containing no induced subgraphs from the set is above or below the Bell number. For properties defined by infinitely many minimal forbidden induced subgraphs, the speed is known to be above the Bell number.
Read More: http://epubs.siam.org/doi/abs/10.1137/15M102421
The combinatorics of resource sharing
We discuss general models of resource-sharing computations, with emphasis on
the combinatorial structures and concepts that underlie the various deadlock
models that have been proposed, the design of algorithms and deadlock-handling
policies, and concurrency issues. These structures are mostly graph-theoretic
in nature, or partially ordered sets for the establishment of priorities among
processes and acquisition orders on resources. We also discuss graph-coloring
concepts as they relate to resource sharing.Comment: R. Correa et alii (eds.), Models for Parallel and Distributed
Computation, pp. 27-52. Kluwer Academic Publishers, Dordrecht, The
Netherlands, 200
Clique covering the edges of a locally cobipartite graph
AbstractWe prove that a locally cobipartite graph on n vertices contains a family of at most n cliques that cover its edges. This is related to Opsut's conjecture that states the competition number of a locally cobipartite graph is at most two