10 citations · 49 across the 34 of their papers we have counts for
22 papers · 1 filter
On -neighborly reorientations of oriented matroids
Rangel Hernández-Ortiz, Kolja Knauer, Luis Pedro Montejano
We study the existence and the number of -neighborly reorientations of an oriented matroid. This leads to -variants of McMullen's problem and Roudneff's conjecture, the case…
Roudneff's Conjecture in Dimension
Rangel Hernández-Ortiz, Kolja Knauer, Luis Pedro Montejano +1
J.-P. Roudneff conjectured in 1991 that every arrangement of pseudohyperplanes in the real projective space has at most $\sum_{i=0}^{d-2} \binom{n-…
A short proof of Kneser's theorem via transversals
Luis Montejano
A very short proof of Kneser's theorem via transversal is given.
Self-dual Maps I : antipodality
Luis Montejano, Jorge L. Ramírez Alfonsín, Ivan Rasskin
A self-dual map is said to be \emph{antipodally self-dual} if the dual map is antipodal embedded in with respect to . In this paper, we investigate nece…
Italian domination in rooted product graphs
R. Hernandez-Ortiz, L. P. Montejano, J. A. Rodriguez-Velazquez
In this article, we obtain closed formulae for the Italian domination number of rooted product graphs. As a particular case of the study, we derive the corresponding formulas for c…
Strongly involutive self-dual polyhedra
Javier Bracho, Luis Montejano, Eric Pauli +1
A polyhedron is a graph which is simple, planar and 3-connected. In this note, we classify the family of strongly involutive self-dual polyhedra. The latter is done by using a…
On the number of vertices of projective polytopes
Natalia García-Colín, Luis Pedro Montejano, Jorge Luis Ramírez Alfonsín
Let be a configuration of points in . What is the maximum number of vertices that can have among all the possible permissible projective transfor…
Rainbow simplices in triangulations of manifolds
Luis Montejano
Given a coloration of the vertices of a triangulation of a manifold, we give homological conditions on the chromatic complexes under which it is possible to obtain a rainbow simple…
Different versions of the nerve theorem and rainbow simplices
Frédéric Meunier, Luis Montejano
Given a simplicial complex and a collection of subcomplexes covering it, the nerve theorem, a fundamental tool in topological combinatorics, guarantees a certain connectivity of th…
Chomp on generalized Kneser graphs and others
Ignacio García-Marco, Kolja Knauer, Luis Pedro Montejano
In chomp on graphs, two players alternatingly pick an edge or a vertex from a graph. The player that cannot move any more loses. The questions one wants to answer for a given graph…
-vectors of chordal graphs
Luis Pedro Montejano, Luis Núñez Betancourt
The -vector of a graph is defined in terms of its clique vector by the equation $\sum^d_{i=1}b_i(x+1)^{i-1}=\sum^d_{i=1} c_i x^{i…
A note on extremal results on directed acyclic graphs
A. Martínez-Pérez, L. Montejano, D. Oliveros
The family of Directed Acyclic Graphs as well as some related graphs are analyzed with respect to extremal behavior in relation with the family of intersection graphs for families…
Complete Kneser Transversals
Jonathan Chappelon, Leonardo Martínez-Sandoval, Luis Montejano +2
Let be integers with . Let be the maximum positive integer such that every set of points (not necessarily in general position) in…
On transversal and -packing numbers in straight line systems on
Gabriela Araujo-Pardo, Amanda Montejano, Luis Montejano +1
A linear system is a pair where is a finite family of subsets on a ground set , and it satisfies that for every pair of distinc…
A geometric Hall-type theorem
Andreas Holmsen, Leonardo Martinez-Sandoval, Luis Montejano
We introduce a geometric generalization of Hall's marriage theorem. For any family of finite sets in , we give conditions under which it is…
The (p,q)-extremal problem and the fractional chromatic number of Kneser hypergraphs
Gabriela Araujo-Pardo, Juan Carlos Díaz-Patiño, Luis Montejano +1
The problem of computing the chromatic number of Kneser hypergraphs has been extensively studied over the last 40 years and the fractional version of the chromatic number of Kneser…
How many circuits determine an oriented matroid?
Kolja Knauer, Luis Pedro Montejano, Jorge Luis Ramírez Alfonsín
Las Vergnas and Hamidoune studied the number of circuits needed to determine an oriented matroid. In this paper we investigate this problem and some new variants, as well as their…
On Ramsey numbers of complete graphs with dropped stars
Jonathan Chappelon, Luis Pedro Montejano, Jorge Ramírez Alfonsín
Let be the smallest integer such that for any -coloring (say, red and blue) of the edges of , , there is either a red copy of or a blue copy…
Ramsey for complete graphs with dropped cliques
Jonathan Chappelon, Luis Pedro Montejano, Jorge Luis Ramírez Alfonsín
Let be the complete graph on vertices from which a set of edges, induced by a clique of order , has been dropped. In this note we give two explicit upper bounds…
Transitive oriented 3-Hypergraphs of cyclic orders
Natalia Garcia-Colin, Amanda Montejano, Luis Montejano +1
In this paper we introduce the definition of transitivity for oriented 3-hypergraphs in order to study partial and complete cyclic orders. This definition allow us to give sufficie…
Order Types of convex bodies
Alfredo Hubard, Luis Montejano, Emiliano Mora +1
We give new bounds on the Erdos-Szekeres theorems for convex bodies of Bisztriczky and Fejes Toth and of Pach and Toth. We derive them from a combinatorial characterization of conv…
Topological transversals to a family of convex sets
L. Montejano, R. N. Karasev
Let be a family of compact convex sets in . We say that has a \emph{topological -transversal of index } (, ) if…