Results 1  10
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19
Counting Triangulations and PseudoTriangulations of Wheels
 IN PROC. 13TH CANAD. CONF. COMPUT. GEOM
, 2001
"... Motivated by several open questions on triangulations and pseudotriangulations, we give closed form expressions for the number of triangulations and the number of minimum pseudotriangulations of n points in wheel configurations, that is, with n  1 in convex position. Although the numbers of trian ..."
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Cited by 21 (5 self)
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Motivated by several open questions on triangulations and pseudotriangulations, we give closed form expressions for the number of triangulations and the number of minimum pseudotriangulations of n points in wheel configurations, that is, with n  1 in convex position. Although the numbers of triangulations and pseudotriangulations vary depending on the placement of the interior point, their difference is always the (n2)nd Catalan number. We also prove an inequality #PT # 3 i #T for the numbers of minimum pseudotriangulations and triangulations of any point configuration with i interior points.
On the Number of CrossingFree Matchings, Cycles, and Partitions
, 2006
"... We show that a set of n points in the plane has at most O(10.05n) perfect matchings with crossingfree straightline embedding. The expected number of perfect crossingfree matchings of a set of n points drawn i.i.d. from an arbitrary distribution in the plane is at most ..."
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Cited by 20 (3 self)
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We show that a set of n points in the plane has at most O(10.05n) perfect matchings with crossingfree straightline embedding. The expected number of perfect crossingfree matchings of a set of n points drawn i.i.d. from an arbitrary distribution in the plane is at most
A Lower Bound on the Number of Triangulations of Planar Point Sets
"... We show that the number of straightedge triangulations exhibited by any set of n points in general position in the plane is bounded from below by 4 :33 ). ..."
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Cited by 14 (3 self)
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We show that the number of straightedge triangulations exhibited by any set of n points in general position in the plane is bounded from below by 4 :33 ).
Boundeddegree graphs have arbitrarily large geometric thickness
, 2008
"... The geometric thickness of a graph G is the minimum integer k such that there is a straight line drawing of G with its edge set partitioned into k plane subgraphs. Eppstein [Separating thickness from geometric thickness. In Towards a Theory of Geometric Graphs, vol. 342 of Contemp. Math., AMS, 200 ..."
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Cited by 14 (6 self)
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The geometric thickness of a graph G is the minimum integer k such that there is a straight line drawing of G with its edge set partitioned into k plane subgraphs. Eppstein [Separating thickness from geometric thickness. In Towards a Theory of Geometric Graphs, vol. 342 of Contemp. Math., AMS, 2004] asked whether every graph of bounded maximum degree has bounded geometric thickness. We answer this question in the negative, by proving that there exists ∆regular graphs with arbitrarily large geometric thickness. In particular, for all ∆ ≥ 9 and for all large n, there exists a ∆regular graph with geometric thickness at least c √ ∆n 1/2−4/∆−ǫ. Analogous results concerning graph drawings with few edge slopes are also presented, thus solving open problems by Dujmović et al. [Really straight graph drawings. In Proc. 12th
Random triangulations of planar points sets
"... Given a set S of n points in the plane, a triangulation is a maximal crossingfree geometric graph on S (in a geometric graph the edges are realized by straight line segments). Here we consider random triangulations, where “random ” refers to uniformly at random from the set of all triangulations of ..."
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Cited by 11 (5 self)
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Given a set S of n points in the plane, a triangulation is a maximal crossingfree geometric graph on S (in a geometric graph the edges are realized by straight line segments). Here we consider random triangulations, where “random ” refers to uniformly at random from the set of all triangulations of S. We are primarily interested in the degree sequences of such random triangulations.
The polytope of noncrossing graphs on a planar point set
, 2003
"... For any finite set A of n points in R 2, we define a (3n − 3)dimensional simple polyhedron whose face poset is isomorphic to the poset of “noncrossing marked graphs” with vertex set A, where a marked graph is defined as a geometric graph together with a subset of its vertices. The poset of noncr ..."
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Cited by 11 (5 self)
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For any finite set A of n points in R 2, we define a (3n − 3)dimensional simple polyhedron whose face poset is isomorphic to the poset of “noncrossing marked graphs” with vertex set A, where a marked graph is defined as a geometric graph together with a subset of its vertices. The poset of noncrossing graphs on A appears as the complement of the star of a face in that polyhedron. The polyhedron has a unique maximal bounded face, of dimension 2ni + n − 3 where ni is the number of points of A in the interior of conv(A). The vertices of this polytope are all the pseudotriangulations of A, and the edges are flips of two types: the traditional diagonal flips (in pseudotriangulations) and the removal or insertion of a single edge. As a byproduct of our construction we prove that all pseudotriangulations are infinitesimally rigid graphs.
Counting Triangulations of Planar Point Sets
"... We study the maximal number of triangulations that a planar set of n points can have, and show that it is at most 30 n. This new bound is achieved by a careful optimization of the charging scheme of Sharir and Welzl (2006), which has led to the previous best upper bound of 43^n for the problem. More ..."
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Cited by 9 (3 self)
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We study the maximal number of triangulations that a planar set of n points can have, and show that it is at most 30 n. This new bound is achieved by a careful optimization of the charging scheme of Sharir and Welzl (2006), which has led to the previous best upper bound of 43^n for the problem. Moreover, this new bound is useful for bounding the number of other types of planar (i.e., crossingfree) straightline graphs on a given point set. Specifically, we derive new upper bounds for the number of planar graphs (O ∗ (239.4 n)), spanning cycles (O ∗ (70.21 n)), spanning trees (160 n), and cyclefree graphs (O ∗ (202.5 n)).
On the number of plane graphs
 PROC. 17TH ANN. ACMSIAM SYMP. ON DISCRETE ALGORITHMS
, 2006
"... We investigate the number of plane geometric, i.e., straightline, graphs, a set S of n points in the plane admits. We show that the number of plane graphs is minimized when S is in convex position, and that the same result holds for several relevant subfamilies. In addition we construct a new extre ..."
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Cited by 8 (1 self)
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We investigate the number of plane geometric, i.e., straightline, graphs, a set S of n points in the plane admits. We show that the number of plane graphs is minimized when S is in convex position, and that the same result holds for several relevant subfamilies. In addition we construct a new extremal configuration, the socalled double zigzag chain. Most noteworthy this example bears Θ ∗ ( √ 72 n) = Θ ∗ (8.4853 n) triangulations and Θ ∗ (41.1889 n) plane graphs (omitting polynomial factors in both cases), improving the previously known best maximizing examples.
On the number of pseudotriangulations of certain point sets
 J. Combin. Theory Ser. A
, 2007
"... We pose a monotonicity conjecture on the number of pseudotriangulations of any planar point set, and check it on two prominent families of point sets, namely the socalled double circle and double chain. The latter has asymptotically 12 n n Θ(1) pointed pseudotriangulations, which lies significant ..."
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Cited by 8 (2 self)
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We pose a monotonicity conjecture on the number of pseudotriangulations of any planar point set, and check it on two prominent families of point sets, namely the socalled double circle and double chain. The latter has asymptotically 12 n n Θ(1) pointed pseudotriangulations, which lies significantly above the maximum number of triangulations in a planar point set known so far. ⋆ Parts of this work were done while the authors visited the Departament de