We provide a method to construct a type of orthomodular structure known as an orthoalgebra from the direct product decompositions of an object in a category that has finite products and whose ternary product diagrams give rise to certain pushouts. This generalizes a method to construct an orthomodular poset from the direct product decompositions of familiar mathematical structures such as non-e...

We show that all finite powers of a Hausdorff space X do not contain uncountable weakly separated subspaces iff there is a c.c.c poset P such that in V P X is a countable union of 0-dimensional subspaces of countable weight. We also show that this theorem is sharp in two different senses: (i) we cannot get rid of using generic extensions, (ii) we have to consider all finite powers of X.

We show that all finite powers of a Hausdorff space X do not contain uncountable weakly separated subspaces iff there is a c.c.c poset P such that in V P X is a countable union of 0-dimensional subspaces of countable weight. We also show that this theorem is sharp in two different senses: (i) we can't get rid of using generic extensions, (ii) we have to consider all finite powers of X.

If S, T are stationary subsets of a regular uncountable cardinal κ, we say that S reflects fully in T , S < T , if for almost all α ∈ T (except a nonstationary set) S ∩ α is stationary in α. This relation is known to be a well-founded partial ordering. We say that a given poset P is realized by the reflection ordering if there is a maximal antichain 〈Xp; p ∈ P 〉 of stationary subsets of Reg(κ) ...

A recent result of Balandraud shows that for every subset S of an abelian group G there exists a non trivial subgroup H such that |TS| ≤ |T |+ |S| − 2 holds only if H ⊂ Stab(TS). Notice that Kneser’s Theorem only gives {0} 6= Stab(TS). This strong form of Kneser’s theorem follows from some nice properties of a certain poset investigated by Balandraud. We consider an analogous poset for nonabeli...

Let Bn be the poset generated by the subsets of [n] with the inclusion as relation and let P be a nite poset. We want to embed P into Bn as many times as possible such that the subsets in di erent copies are incomparable. The maximum number of such embeddings is asymptotically determined for all nite posets P as 1 t(P ) ( n bn/2c ) , where t(P ) denotes the minimal size of the convex hull of a ...

Empty p0 p2 . . . pξ pξ+2 . . . Nonempty p1 p3 . . . pξ+1 pξ+3 . . . where pξ, ξ < α, is descending in P and Nonempty wins the game of length α if he can play α times. A poset P is called weakly α-game-closed if Player Nonempty has a winning strategy in the Banach-Mazur game of length α, where Nonempty is allowed to play at limit stages. P is called strongly α-game-closed if Player Nonempty has...

Building everything from scratch, we give another proof of Propp and Roby’s theorem saying that the average antichain size in any reverse operator orbit of the poset [m] × [n] is mn m+n . It is conceivable that our method should work for other situations. As a demonstration, we show that the average size of antichains in any reverse operator orbit of [m] ×Kn−1 equals 2mn m+2n−1 . Here Kn−1 is t...

the notion of a $d$-poset was introduced in a connection withquantum mechanical models. in this paper, we introduce theconditional expectation of  random variables on thek^{o}pka's $d$-poset and prove the basic properties ofconditional expectation on this  structure.

In this paper, the poset $BX$ of formal balls is studied in fuzzy partial metric space $(X,p,*)$. We introduce the notion of layered complete fuzzy partial metric space and get that the poset $BX$ of formal balls is a dcpo if and only if $(X,p,*)$ is layered complete fuzzy partial metric space.