68,165 research outputs found
Two relations for median graphs
AbstractWe generalize the well-known relation for trees nām=1 to the class of median graphs in the following way. Denote by qi the number of subgraphs isomorphic to the hypercube Qi in a median graph. Then, āiā©¾0(ā1)iqi=1. We also give an explicit formula for the number of Ī-classes in a median graph as k=āāiā©¾0(ā1)iiqi
Recognizing Partial Cubes in Quadratic Time
We show how to test whether a graph with n vertices and m edges is a partial
cube, and if so how to find a distance-preserving embedding of the graph into a
hypercube, in the near-optimal time bound O(n^2), improving previous O(nm)-time
solutions.Comment: 25 pages, five figures. This version significantly expands previous
versions, including a new report on an implementation of the algorithm and
experiments with i
Query-based extracting: how to support the answer?
Human-made query-based summaries commonly contain information not explicitly asked for. They answer the user query, but also provide supporting information. In order to find this information in the source text, a graph is used to model the strength and type of relations between sentences of the query and document cluster, based on various features. The resulting extracts rank second in overall readability in the DUC 2006 evaluation. Employment of better question answering methods is the key to improve also content-based evaluation results
Groups acting on quasi-median graphs. An introduction
Quasi-median graphs have been introduced by Mulder in 1980 as a
generalisation of median graphs, known in geometric group theory to naturally
coincide with the class of CAT(0) cube complexes. In his PhD thesis, the author
showed that quasi-median graphs may be useful to study groups as well. In the
present paper, we propose a gentle introduction to the theory of groups acting
on quasi-median graphs.Comment: 16 pages. Comments are welcom
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