On the discrepancy of quasi-progressions.
On the Hypercompetition Numbers of Hypergraphs with Maximum Degree at Most Two
In this note, we give an easy and short proof for the theorem by Park and Kim stating that the hypercompetition numbers of hypergraphs with maximum degree at most two is at most two.
On the rainbow connection of Cartesian products and their subgraphs
Rainbow connection number of Cartesian products and their subgraphs are considered. Previously known bounds are compared and non-existence of such bounds for subgraphs of products are discussed. It is shown that the rainbow connection number of an isometric subgraph of a hypercube is bounded above by the rainbow connection number of the hypercube. Isometric subgraphs of hypercubes with the rainbow connection number as small as possible compared to the rainbow connection of the hypercube are constructed....
On the size of minimal unsatisfiable formulas.
On the upper and lower chromatic numbers of BSQSs(16).
On total matching numbers and total covering numbers for -uniform hypergraphs
On tours that contain all edges of a hypergraph.
On uniquely partitionable relational structures and object systems
We introduce object systems as a common generalization of graphs, hypergraphs, digraphs and relational structures. Let C be a concrete category, a simple object system over C is an ordered pair S = (V,E), where E = A₁,A₂,...,Aₘ is a finite set of the objects of C, such that the ground-set of each object is a finite set with at least two elements and . To generalize the results on graph colourings to simple object systems we define, analogously as for graphs, that an additive induced-hereditary...
One More Turán Number and Ramsey Number for the Loose 3-Uniform Path of Length Three
Let P denote a 3-uniform hypergraph consisting of 7 vertices a, b, c, d, e, f, g and 3 edges {a, b, c}, {c, d, e}, and {e, f, g}. It is known that the r-color Ramsey number for P is R(P; r) = r + 6 for r ≤ 9. The proof of this result relies on a careful analysis of the Turán numbers for P. In this paper, we refine this analysis further and compute the fifth order Turán number for P, for all n. Using this number for n = 16, we confirm the formula R(P; 10) = 16.
Optimal Betti numbers of forest ideals.