8 citations · 12 across the 9 of their papers we have counts for
11 papers
The diachromatic number of digraphs
Gabriela Araujo-Pardo, Juan José Montellano-Ballesteros, Mika Olsen +1
We consider the extension to directed graphs of the concept of achromatic number in terms of acyclic vertex colorings. The achromatic number have been intensely studied since it wa…
Some heterochromatic theorems for matroids
Criel Merino, Juan José Montellano-Ballesteros
The anti-Ramsey number of Erdös, Simonovits and Sós from 1973 has become a classic invariant in Graph Theory. To study this invariant in Matroid Theory, we use a related invariant…
The strong convexity spectra of grids
Gabriela Araujo-Pardo, César Hernández-Cruz, Juan José Montellano-Ballesteros
Let be a connected oriented graph. A set is convex in if, for every pair of vertices , the vertex set of every -geodesic, ( shortest…
Mixed Cages
G. Araujo-Pardo, C. Hernández-Cruz, J. J. Montellano-Ballesteros
We introduce the notion of a -mixed cage. A -mixed cage is a mixed graph , -regular by arcs, -regular by edges, with girth and minimum order. In…
On heterochromatic out-directed spanning trees in tournaments
Juan José Montellano-Ballesteros, Eduardo Rivera Campo
Given a tournament T, let h(T) be the smallest integer k such that every arc-coloring of T with k or more colors produces at least one out-directed spanning tree of T with no pair…
On the pseudoachromatic index of the complete graph III
G. Araujo-Pardo, J. J. Montellano-Ballesteros, C. Rubio-Montiel +1
Let be the projective plane of order , let the pseudoachromatic number of the complete line graph of order , let $ a\in \{ 3,4,\dots,\tfrac{q}{2…
Rainbow connection in some digraphs
Jesús Alva-Samos, Juan José Montellano-Ballesteros
An edge-coloured graph is {\it rainbow connected} if any two vertices are connected by a path whose edges have distinct colours. This concept was introduced by Chartrand et al.…
k-colored kernels
Hortensia Galeana-Sánchez, Bernardo Llano, Juan José Montellano-Ballesteros
We study -colored kernels in -colored digraphs. An -colored digraph has -colored kernel if there exists a subset of its vertices such that (i) from every vertex…
A graph-theoretical axiomatization of oriented matroids
Kolja Knauer, Juan Jose Montellano-Ballesteros, Ricardo Strausz
We characterize which systems of sign vectors are the cocircuits of an oriented matroid in terms of the cocircuit graph.
On the heterochromatic number of hypergraphs associated to geometric graphs and to matroids
Juan José Montellano-Ballesteros, Eduardo Rivera-Campo
The heterochromatic number hc(H) of a non-empty hypergraph H is the smallest integer k such that for every colouring of the vertices of H with exactly k colours, there is a hypered…
Cubic Time Recognition of Cocircuit Graphs of Uniform Oriented Matroids
Stefan Felsner, Ricardo Gomez, Kolja Knauer +2
We present an algorithm which takes a graph as input and decides in cubic time if the graph is the cocircuit graph of a uniform oriented matroid. In the affirmative case the algori…