VE I) be a family of such intervals. For NE I let V(N) be the chromatic number of the intersection graph 0; (A,,: Y E N), Theorem 1. Zf I is finite and A,, f1.4,,#0 for CL, YE I, tlren n,,, A# 6 Theorem 2. Let k IX a positiw integer and x(N) G k for INI = k + 1. Then x(Z) c k. XlleOrean 3. There is
Interval orders based on arbitrary ordered sets
β Scribed by Jutta Mitas
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 923 KB
- Volume
- 144
- Category
- Article
- ISSN
- 0012-365X
No coin nor oath required. For personal study only.
β¦ Synopsis
In general, an interval order is defined to be an ordered set which has an interval representation on a linearly ordered set, the real numbers for example. Bogart et al. (1991) generalized this concept and allowed the underlying set to be weakly ordered. They found a necessary and sufficient condition for an ordered set to be an interval order based on a weak order as well as a characterization for this class of ordered sets by 4 forbidden suborders. In this paper interval orders based on further classes of ordered sets are investigated. Hereby, we concentrate on classes characterized by one forbidden suborder, such as series-parallel orders and interval orders. Furthermore, we analyse connections between order dimension and interval dimension.
π SIMILAR VOLUMES
## L dimension may be chosen within each of the subspaces L in the set S that are ''in general position.'' For example, in the real projective space of dimension 3, consider a plane , a line r not belonging to , the point P [ r l , and two distinct points Q, R both different from P, lying on the l
We show that a proper coloring of the diagram of an interval order I may require 1 + I-log 2 height(l)] colors and that 2 + l-log 2 height(I)'] colors always suffice. For the proof of the upper bound we use the following fact: A sequence C 1 ... ## .. C h of sets (of colors) with the property (ct) C