The connection matrix theory for semiflows on (not necessarily locally compact) metric spaces

AbstractThe index theory of Rybakowski for isolated invariant sets and attractor-repeller pairs in the setting of a semiflow on a not necessarily locally compact metric space is extended to include a connection matrix theory for Morse decompositions. Partially ordered Morse decompositions and attractor semifiltrations of invariant sets are defined and shown to be equivalent. The definition and proof of existence of index filtrations for an ordered Morse decomposition is provided. Via the index filtration, the homology index braid and the connection matrices of the Morse decomposition are defined

Decompositions of Modules Associated to Finite Partially Ordered Sets

AbstractFor a finite partially ordered set L and a field F, let F L be the associated vector space with L as basis. In the case of ranked posets this space decomposes into eigenspaces under the maps afforded by the order relation. In this note we show how to construct generating sets for such decompositions and discuss their combinatorial significance

Type-Decomposition of a Pseudo-Effect Algebra

The theory of direct decomposition of a centrally orthocomplete effect algebra into direct summands of various types utilizes the notion of a type-determining (TD) set. A pseudo-effect algebra (PEA) is a (possibly) noncommutative version of an effect algebra. In this article we develop the basic theory of centrally orthocomplete PEAs, generalize the notion of a TD set to PEAs, and show that TD sets induce decompositions of centrally orthocomplete PEAs into direct summands.Comment: 18 page

Measurable realizations of abstract systems of congruences

An abstract system of congruences describes a way of partitioning a space into finitely many pieces satisfying certain congruence relations. Examples of abstract systems of congruences include paradoxical decompositions and $n$-divisibility of actions. We consider the general question of when there are realizations of abstract systems of congruences satisfying various measurability constraints. We completely characterize which abstract systems of congruences can be realized by nonmeager Baire measurable pieces of the sphere under the action of rotations on the $2$-sphere. This answers a question of Wagon. We also construct Borel realizations of abstract systems of congruences for the action of $\mathsf{PSL}_2(\mathbb{Z})$ on $\mathsf{P}^1(\mathbb{R})$. The combinatorial underpinnings of our proof are certain types of decomposition of Borel graphs into paths. We also use these decompositions to obtain some results about measurable unfriendly colorings.Comment: minor correction