It was proved by Juhász and Weiss that for every ordinal α with $0<\alpha <{\omega }_2$ there is a superatomic Boolean algebra of height α and width ω. We prove that if κ is an infinite cardinal such that ${\kappa }^{<\kappa }=\kappa$ and α is an ordinal such that $0<\alpha <{\kappa }^{++}$, then there is a cardinal-preserving partial order that forces the existence of a superatomic Boolean algebra of height α and width κ. Furthermore, iterating this forcing through all $\alpha <{\kappa }^{++}$, we obtain a notion of forcing that preserves cardinals and such that in the corresponding generic...

Let G(X) denote the smallest (von Neumann) regular ring of real-valued functions with domain X that contains C(X), the ring of continuous real-valued functions on a Tikhonov topological space (X,τ). We investigate when G(X) coincides with the ring $C(X,{\tau }_{\delta })$ of continuous real-valued functions on the space $(X,{\tau }_{\delta })$, where ${\tau }_{\delta }$ is the smallest Tikhonov topology on X for which $\tau \subseteq {\tau }_{\delta }$ and $C(X,{\tau }_{\delta })$ is von Neumann regular. The compact and metric spaces for which $G\left(X\right)=C(X,{\tau }_{\delta })$ are characterized. Necessary, and different sufficient, conditions...

A space $X$ is functionally countable if $f\left(X\right)$ is countable for any continuous function $f:X\to ℝ$. We will call a space $X$ exponentially separable if for any countable family $ℱ$ of closed subsets of $X$, there exists a countable set $A\subset X$ such that $A\cap \bigcap 𝒢\ne \varnothing$ whenever $𝒢\subset ℱ$ and $\bigcap 𝒢\ne \varnothing$. Every exponentially separable space is functionally countable; we will show that for some nice classes of spaces exponential separability coincides with functional countability. We will also establish that the class of exponentially separable spaces has...

We show that every Lipschitz map defined on an open subset of the Banach space C(K), where K is a scattered compactum, with values in a Banach space with the Radon-Nikodym property, has a point of Fréchet differentiability. This is a strengthening of the result of Lindenstrauss and Preiss who proved that for countable compacta. As a consequence of the above and a result of Arvanitakis we prove that Lipschitz functions on certain function spaces are Gâteaux differentiable.

Let $(L,\le )$, be an algebraic lattice. It is well-known that $(L,\le )$ with its topological structure is topologically scattered if and only if $(L,\le )$ is ordered scattered with respect to its algebraic structure. In this note we prove that, if $L$ is a distributive algebraic lattice in which every element is the infimum of finitely many primes, then $L$ has Krull-dimension if and only if $L$ has derived dimension. We also prove the same result for $errorL$, the set of all prime elements of $L$. Hence the dimensions on the lattice...