Zobrazeno 1 - 5
of 5
pro vyhledávání: '"Johanna Wiehe"'
Publikováno v:
AKCE International Journal of Graphs and Combinatorics, Vol 17, Iss 3, Pp 992-994 (2020)
Reed (1987) showed that, if two graphs are P4-isomorphic, then either both are perfect or none of them is. In this note, we will derive an analogous result for perfect digraphs.
Externí odkaz:
https://doaj.org/article/4e24ce3cca934cb78686094340005656
Publikováno v:
AKCE International Journal of Graphs and Combinatorics, Vol 17, Iss 3, Pp 992-994 (2020)
Reed showed that, if two graphs are $P_4$-isomorphic, then either both are perfect or none of them is. In this note we will derive an analogous result for perfect digraphs.
5 pages, 1 figure
5 pages, 1 figure
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::412a907d6fc5663311211f4c82deb029
https://doi.org/10.1016/j.akcej.2019.12.018
https://doi.org/10.1016/j.akcej.2019.12.018
Autor:
Winfried Hochstättler, Johanna Wiehe
Publikováno v:
Trends in Mathematics ISBN: 9783030838225
We define a trivariate polynomial combining the NL-coflow and the NL-flow polynomial, which build a dual pair counting acyclic colorings of directed graphs, in the more general setting of regular oriented matroids.
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_________::8d2d2792578d28104bb311dd4f36a1a9
https://doi.org/10.1007/978-3-030-83823-2_59
https://doi.org/10.1007/978-3-030-83823-2_59
Autor:
Johanna Wiehe, Winfried Hochstättler
Publikováno v:
AIRO Springer Series ISBN: 9783030630713
An acyclic coloring of a digraph as defined by V. Neumann-Lara is a vertex-coloring such that no monochromatic directed cycles occur. Counting the number of such colorings with k colors can be done by counting so-called Neumann-Lara-coflows (NL-coflo
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_________::075ac770b39c4b3d63a2abc52ae79b55
https://doi.org/10.1007/978-3-030-63072-0_1
https://doi.org/10.1007/978-3-030-63072-0_1
In 1982 V\'{i}ctor Neumann-Lara introduced the dichromatic number of a digraph $D$ as the smallest integer $k$ such that the vertices $V$ of $D$ can be colored with $k$ colors and each color class induces an acyclic digraph. Later a flow theory for t
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::0ff3c115b3756420faa2ad6467a6e642