7 research outputs found
The Maximum Chromatic Number of the Disjointness Graph of Segments on -point Sets in the Plane with
Let be a finite set of points in general position in the plane. The
disjointness graph of segments of is the graph whose vertices are
all the closed straight line segments with endpoints in , two of which are
adjacent in if and only if they are disjoint. As usual, we use
to denote the chromatic number of , and use to denote
the maximum taken over all sets of points in general
position in the plane. In this paper we show that if and only if
.Comment: 25 pages, 3 figure
A convex decomposition
Dada una colección P de puntos en el plano, una descomposición convexa de P es un conjunto de polÃgonos convexos con vértices en P que satisfacen lo siguiente: La unión de todos los elementos de es el cierre convexo de P, cada elemento de es vacÃo (no contiene a ningún otro elemento de P en su interior) y para cualesquiera 2 elementos diferentes en sus interiores son disjuntos (se intersecarán en a lo más una arista). Únicamente se sabe que existen descomposiciones convexas con a lo más 7n/5 elementos para toda colección de n puntos. En este trabajo diremos cómo obtener una descomposición convexa especÃfica de P con a lo más 3n/2 elementos.
Para citar este artÃculo: M. LomelÃ-Haro, V. Borja, J.A. Hernández, Una descomposición convexa, Rev. Integr. Temas Mat. 32 (2014), no. 2, 169-180.Given a point set P on the plane, a convex decomposition of P is a set of convex polygons with vertices in P satisfying the following conditions: The union of all elements in is the convex hull of P, every element in is empty (that is, they no contain any element of P in its interior), and any given 2 elements in its interiors are disjoint intersecting them in at most one edge. It is known that if P has n elements, then there exists a convex decomposition of P with at most 7n/5 elements. In this work we give a procedure to find a specific convex decomposition of P with at most 3n/2 elements.
To cite this article: M. LomelÃ-Haro, V. Borja, J.A. Hernández, Una descomposición convexa, Rev. Integr. Temas Mat. 32 (2014), no. 2, 169-180.
 
Una descomposición convexa
Dada una colección P de puntos en el plano, una descomposición convexa de P es un conjunto Γ de polÃgonos convexos convértices en P que satisfacen lo siguiente: La unión de todos los elementos de Γ es el cierre convexo de P, cada elemento de Γ es vacÃo (no contiene a ningún otro elemento de P en su interior) y para cualesquiera 2 elementos diferentes en Γ sus interiores son disjuntos (se intersecarán en a lo más una arista). Únicamente se sabe que existen descomposiciones convexas con a lo más 7n/5 elementos para toda colección de n puntos. En este trabajo diremos cómo obtener una descomposición convexa especÃfica de P con a lo más 3n/ 2 elementos
The Chromatic Number of the Disjointness Graph of the Double Chain
Let be a set of points in general position in the plane.
Consider all the closed straight line segments with both endpoints in .
Suppose that these segments are colored with the rule that disjoint segments
receive different colors. In this paper we show that if is the point
configuration known as the double chain, with points in the upper convex
chain and points in the lower convex chain, then colors are needed and that
this number is sufficient
The Chromatic Number of the Disjointness Graph of the Double Chain
Let be a set of points in general position in the plane.Consider all the closed straight line segments with both endpoints in .Suppose that these segments are colored with the rule that disjoint segmentsreceive different colors. In this paper we show that if is the pointconfiguration known as the double chain, with points in the upper convexchain and points in the lower convex chain, then colors are needed and thatthis number is sufficient