3 papers
math.CO2019
Complete Acyclic Colorings
Stefan Felsner, Winfried Hochstättler, Kolja Knauer +1
We study two parameters that arise from the dichromatic number and the vertex-arboricity in the same way that the achromatic number comes from the chromatic number. The adichromati…
math.CO2019
The NL-flow polynomial
Barbara Altenbokum, Winfried Hochstättler, Johanna Wiehe
In 1982 Víctor Neumann-Lara introduced the dichromatic number of a digraph as the smallest integer such that the vertices of can be colored with colors and each…
math.CO2018
The Varchenko Determinant for Oriented Matroids
Winfried Hochstättler, Volkmar Welker
We generalize the Varchenko matrix of a hyperplane arrangement to oriented matroids. We show that the celebrated determinant formula for the Varchenko matrix, first proved by Varch…