منابع مشابه
Visibility Graphs of Towers
A tower is a polygon consisting of two reflex chains sharing one common endpoint, together with one edge joining the other endpoints of the chains. A linear time algorithm is given to recognize the [vertex] visibility graphs of towers, and these graphs are characterized as bipartite permutation graphs with an added Hamiltonian cycle. Similar results have been obtained independently by Choi, Shi...
متن کاملStrong approximation in random towers of graphs
The term strong approximation is used to describe phenomena where an arithmetic group as well as all of its Zariski dense subgroups have a large image in the congruence quotients. We exhibit analogues of such phenomena in a probabilistic, rather than arithmetic, setting. Let T be the binary rooted tree, Aut(T ) its automorphism group. To a given m-tuple a = {a1, a2, . . . , am} ∈ Aut(T ) we ass...
متن کاملBAR k-VISIBILITY GRAPHS
Die selbständige und eigenhändige Anfertigung versichere ich an Eides statt. Conclusion 71 Bibliography 75 Introduction " The true mystery of the world is the visible, not the invisible. " Oscar Wilde How can geometric settings be encoded combinatorially? Which discrete structures extract the essential information from continuous arrangements? How can the combinatorial properties of visibility ...
متن کاملVisibility Graphs and Oriented
We describe a set of necessary conditions for a given graph to be the visibility graph of a simple polygon. For every graph satisfying these conditions we show that a uniform rank 3 oriented matroid can be constructed in polynomial time, which if affinely coordinatizable yields a simple polygon whose visibility graph is isomorphic to the given graph.
متن کاملOn k-visibility graphs
We examine several types of visibility graphs in which sightlines can pass through k objects. For k ≥ 1 we bound the maximum thickness of semi-bar k-visibility graphs between d 2 3 (k + 1)e and 2k. In addition we show that the maximum number of edges in arc and circle k-visibility graphs on n vertices is at most (k+1)(3n− k− 2) for n > 4k+4 and ( n 2 ) for n ≤ 4k + 4, while the maximum chromati...
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ژورنال
عنوان ژورنال: Computational Geometry
سال: 1997
ISSN: 0925-7721
DOI: 10.1016/0925-7721(95)00033-x