Resumen In this paper we review recent results on a new variation of the Art Gallery problem. A common problem we face nowadays, is that of placing a set of wireless modems in a building in such a way that a computer placed anywhere within the building receives a signal strong enough to connect to the Web. In most buildings, the main limitation for this… (More)
We study a geometric Ramsey type problem where the vertices of the complete graph K n are placed on a set S of n points in general position in the plane, and edges are drawn as straight-line segments. We define the empty convex polygon Ramsey number R EC (k, k) as the smallest number n such that for every set S of n points and for every two-coloring of the… (More)
Let S be a 2-colored (red and blue) set of n points in the plane. A subset I of S is an island if there exits a convex set C such that I = C ∩S. The discrepancy of an island is the absolute value of the number of red minus the number of blue points it contains. A convex partition of S is a partition of S into islands with pairwise disjoint convex hulls. The… (More)
We study the number of crossings among edges of some higher order proximity graphs of the family of the Delaunay graph. That is, given a set P of n points in the Euclidean plane, we give lower and upper bounds on the minimum and the maximum number of crossings that these geometric graphs defined on P have.
We consider a variation of a problem stated by Erdös and Guy in 1973 about the number of convex k-gons determined by any set S of n points in the plane. In our setting the points of S are colored and we say that a spanned polygon is monochromatic if all its points are colored with the same color. As a main result we show that any bi-colored set of n points… (More)
This paper studies the chromatic number of the following four flip graphs (under suitable definitions of a flip): • the flip graph of perfect matchings of a complete graph of even order, • the flip graph of triangulations of a convex polygon (the associahedron), • the flip graph of non-crossing Hamiltonian paths of a convex point set, and • the flip graph… (More)