-Polaren in halbgeordneten Mengen
Martin's axiom and partitions
Maximal antichains in a partially ordered set
Maximal subsemilattices of the full transformation semigroup on a finite set [Book]
Measurability of functions with values in partially ordered spaces
Measurable spaces with c.c.c. [Book]
Methods of calculating cohomological and Hochschild-Mitchell dimensions of finite partially ordered sets.
Möbius inversion for the Bruhat ordering on a Weyl group
Modular ordered sets
Modular posets and semigroups.
Modulare Inzidenzstrukturen
Monotone and cone preserving mappings on posets
We define several sorts of mappings on a poset like monotone, strictly monotone, upper cone preserving and variants of these. Our aim is to study in which posets some of these mappings coincide. We define special mappings determined by two elements and investigate when these are strictly monotone or upper cone preserving. If the considered poset is a semilattice then its monotone mappings coincide with semilattice homomorphisms if and only if the poset is a chain. Similarly, we study posets which...
More on the complexity of cover graphs
In response to [3] and [4] we prove that the recognition of cover graphs of finite posets is an NP-hard problem.
More set-theory around the weak Freese–Nation property
We introduce a very weak version of the square principle which may hold even under failure of the generalized continuum hypothesis. Under this weak square principle, we give a new characterization (Theorem 10) of partial orderings with κ-Freese-Nation property (see below for the definition). The characterization is not a ZFC theorem: assuming Chang’s Conjecture for , we can find a counter-example to the characterization (Theorem 12). We then show that, in the model obtained by adding Cohen reals,...
Multiabbildungen und Anordnungen der Mengen