Results 1  10
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18
Lenses in arrangements of pseudocircles and their applications
 J. ACM
, 2004
"... Abstract. A collection of simple closed Jordan curves in the plane is called a family of pseudocircles if any two of its members intersect at most twice. A closed curve composed of two subarcs of distinct Work on this article by P. Agarwal, J. Pach, and M. Sharir has been supported by a joint grant ..."
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Cited by 24 (10 self)
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Abstract. A collection of simple closed Jordan curves in the plane is called a family of pseudocircles if any two of its members intersect at most twice. A closed curve composed of two subarcs of distinct Work on this article by P. Agarwal, J. Pach, and M. Sharir has been supported by a joint grant from the U.S.–Israel Binational Science Foundation. Work by P. Agarwal has also been supported by NSF grants EIA9870724, EIA9972879, ITR333
On Levels in Arrangements of Curves
 Proc. 41st IEEE
, 2002
"... Analyzing the worstcase complexity of the klevel in a planar arrangement of n curves is a fundamental problem in combinatorial geometry. We give the first subquadratic upper bound (roughly O(nk 9 2 s 3 )) for curves that are graphs of polynomial functions of an arbitrary fixed degree s. Previously ..."
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Cited by 23 (3 self)
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Analyzing the worstcase complexity of the klevel in a planar arrangement of n curves is a fundamental problem in combinatorial geometry. We give the first subquadratic upper bound (roughly O(nk 9 2 s 3 )) for curves that are graphs of polynomial functions of an arbitrary fixed degree s. Previously, nontrivial results were known only for the case s = 1 and s = 2. We also improve the earlier bound for pseudoparabolas (curves that pairwise intersect at most twice) to O(nk k). The proofs are simple and rely on a theorem of Tamaki and Tokuyama on cutting pseudoparabolas into pseudosegments, as well as a new observation for cutting pseudosegments into pieces that can be extended to pseudolines. We mention applications to parametric and kinetic minimum spanning trees.
On the Number of Congruent Simplices in a Point Set
 DISCRETE & COMPUTATIONAL GEOMETRY
, 2002
"... We derive improved bounds on the number of kdimensional simplices spanned by a set of n points in R(sup d) that are congruent to a given ksimplex, for k < or = d  1. Let f(sup d)(sub K)(n) be the maximum number of ksimplices spanned by a set of n points in R(sup d) that are congruent to a given ..."
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Cited by 12 (2 self)
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We derive improved bounds on the number of kdimensional simplices spanned by a set of n points in R(sup d) that are congruent to a given ksimplex, for k < or = d  1. Let f(sup d)(sub K)(n) be the maximum number of ksimplices spanned by a set of n points in R(sup d) that are congruent to a given ksimplex. We prove that f(sup 3)(sub 2) (n) = O(n sup 5/3) times 2 sup O(alpha (sup 2)(n)), f(sup 4)(sub 2)(n) = O(n (sup 2) + epsilon), f(sup 5)(sub 2) (n)) = theta (n (sup 7/3), and f(sup 4)(sub 3)(n) = O(n (sup 9/4) plus epsilon). We also derive a recurrence to bound f(sup d)(sub k) (n) for arbitrary values of k and d, and use it to derive the bound f(sup d)(sub k(n) = O(n(sup d/2)) for d < or = 7 and k < or = d  2. Following Erdo's and Purdy, we conjecture that this bound holds for larger values of d as well, and for k < or = d  2.
Pseudoline arrangements: Duality. algorithms and applications
 SIAM J. Comput
, 2001
"... A collection L of xmonotone unbounded Jordan curves in the plane is called a family of pseudolines if every pair of curves intersects in at most one point, and the two curves cross each other there. Let P be a set of points in R 2. We define a duality transform that maps L to a set L of points in R ..."
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Cited by 12 (5 self)
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A collection L of xmonotone unbounded Jordan curves in the plane is called a family of pseudolines if every pair of curves intersects in at most one point, and the two curves cross each other there. Let P be a set of points in R 2. We define a duality transform that maps L to a set L of points in R 2 and P to a set
Incidences between points and circles in three and higher dimensions
 Geom
, 2002
"... We show that the number of incidences between m distinct points and n distinct circles in R d, for any d ≥ 3, is O(m 6/11 n 9/11 κ(m 3 /n)+m 2/3 n 2/3 +m+n), where κ(n) = (log n) O(α2 (n)) and where α(n) is the inverse Ackermann function. The bound coincides with the recent bound of Aronov and Shar ..."
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Cited by 11 (7 self)
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We show that the number of incidences between m distinct points and n distinct circles in R d, for any d ≥ 3, is O(m 6/11 n 9/11 κ(m 3 /n)+m 2/3 n 2/3 +m+n), where κ(n) = (log n) O(α2 (n)) and where α(n) is the inverse Ackermann function. The bound coincides with the recent bound of Aronov and Sharir, or rather with its slight improvement by Agarwal et al., for the planar case. We also show that the number of incidences between m points and n unrestricted convex (or boundeddegree algebraic) plane curves, no two in a common plane, is O(m 4/7 n 17/21 + m 2/3 n 2/3 + m + n), in any dimension d ≥ 3. Our results improve the upper bound on the number of congruent copies of a fixed tetrahedron in a set of n points in 4space and the lower bound for the number of distinct distances in a set of n points in 3space. Another application is an improved bound for the number of incidences (or, rather, containments) between lines and reguli in three dimensions. The latter result has already been applied by Feldman and Sharir to obtain a new bound on the number of joints in an arrangement of lines in three dimensions.
On the complexity of many faces in arrangements of pseudosegments and
 of circles, in Discrete and Computational Geometry: The GoodmanPollack Festschrift
"... We obtain improved bounds on the complexity of m distinct faces in an arrangement of n pseudosegments, n circles, or n unit circles. The bounds are worstcase optimal for unit circles; they are also worstcase optimal for the case of pseudosegments, except when the number of faces is very small, i ..."
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Cited by 9 (5 self)
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We obtain improved bounds on the complexity of m distinct faces in an arrangement of n pseudosegments, n circles, or n unit circles. The bounds are worstcase optimal for unit circles; they are also worstcase optimal for the case of pseudosegments, except when the number of faces is very small, in which case our upper bound is a polylogarithmic factor from the bestknown lower bound. For general circles, the bounds nearly coincide with the bestknown bounds for the number of incidences between m points and n circles, recently obtained in [9]. 1
Isosceles Triangles Determined By a Planar Point Set
"... It is proved that, for any " > 0 and n > n 0 ("), every set of n points in the plane has at most n 5e 1 + triples that induce isosceles triangles. (Here e denotes the base of the natural logarithm, so the exponent is roughly 2:136.) This easily implies the best currently known lower bound, n 5 ..."
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Cited by 8 (2 self)
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It is proved that, for any " > 0 and n > n 0 ("), every set of n points in the plane has at most n 5e 1 + triples that induce isosceles triangles. (Here e denotes the base of the natural logarithm, so the exponent is roughly 2:136.) This easily implies the best currently known lower bound, n 5e 1 , for the smallest number of distinct distances determined by n points in the plane, due to Solymosi{C. Toth and Tardos.
PointLine Incidences in Space
, 2002
"... Given a set L of n lines in R , joints are points in R that are incident to at least three noncoplanar lines in L. We show that there are at most O(n ) incidences between L and the set of its joints. ..."
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Cited by 5 (4 self)
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Given a set L of n lines in R , joints are points in R that are incident to at least three noncoplanar lines in L. We show that there are at most O(n ) incidences between L and the set of its joints.
Similar Simplices in a dDimensional Point Set
, 2007
"... We consider the problem of bounding the maximum possible number fk,d(n) of ksimplices that are spanned by a set of n points in R d and are similar to a given simplex. We first show that f2,3(n) = O(n 13/6), and then tackle the general case, and show that fd−2,d(n) = O(n d−8/5) and 1 fd−1,d(n) = O ..."
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Cited by 4 (2 self)
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We consider the problem of bounding the maximum possible number fk,d(n) of ksimplices that are spanned by a set of n points in R d and are similar to a given simplex. We first show that f2,3(n) = O(n 13/6), and then tackle the general case, and show that fd−2,d(n) = O(n d−8/5) and 1 fd−1,d(n) = O ∗ (n d−72/55), for any d. Our technique extends to derive bounds for other values of k and d, and we illustrate this by showing that f2,5(n) = O(n 8/3).