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Kevin Abela

Publications and source records attributed to Kevin Abela.

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Lattice uniformities inducing unbounded convergence

A net $(x_γ)_{γ\inΓ}$ in a locally solid Riesz space $(X,τ)$ is said to be unbounded $τ$-convergent to $x$ if $|x_γ-x|\wedge u\mathop{\oversetτ{\longrightarrow}} 0$ for all $u\in X_+$. We recall that there is a locally solid linear topology $\mathfrak{u}τ$ on $X$ such that unbounded $τ$-convergence coincides with $\mathfrak{u}τ$-convergence, and moreover, $\mathfrak{u}τ$ is characterised as the weakest locally solid linear topology which coincides with $τ$ on all order bounded subsets. It is with this motivation that we introduce, for a uniform lattice $(L,u)$, the weakest lattice uniformity $u^\ast$ on $L$ that coincides with $u$ on all the order bounded subsets of $L$. It is shown that if $u$ is the uniformity induced by the topology of a locally solid Riesz space $(X,τ)$, then the $u^*$-topology coincides with $\mathfrak{u}τ$. This allows comparing the results of this paper with earlier results on unbounded $τ$-convergence. It will be seen that despite the fact that in the setup of uniform lattices most of the machinery used in the techniques of [M. A. Taylor 2019: Unbounded topologies and uo-convergence in locally solid vector spaces, J. Math. Anal. Appl. \bf{472} no.1, 981--1000] is lacking, the concept of `unbounded convergence' well fittingly generalizes to uniform lattices. We shall also answer Questions 2.13, 3.3, 5.10 of [M. A. Taylor 2019: Unbounded topologies and uo-convergence in locally solid vector spaces, J. Math. Anal. Appl. \bf{472} no.1, 981--1000] and Question 18.51 of [M. A. Taylor 2018: Unbounded convergence in vector lattices, Thesis University of Alberta].

math.FA

On different modes of order convergence and some applications

Different notions for order convergence have been considered by various authors. Associated to every notion of order convergence corresponds a topology, defined by taking as the closed sets those subsets of the poset satisfying that no net in them order converges to a point that is outside of the set. We shall give a thorough overview of these different notions and provide a systematic comparison of the associated topologies. Then, in the last section we shall give an application of this study by giving a result on von Neumann algebras complementing the study started in \cite{ChHaWe}. We show that for every atomic von Neumann algebra (not necessarily $σ$-finite) the restriction of the order topology to bounded parts of $M$ coincides with the restriction of the $σ$-strong topology $s(M,M_\ast)$. We recall that the methods of \cite{ChHaWe} rest heavily on the assumption of $σ$-finiteness. Further to this, for a semi-finite measure space, we shall give a complete picture of the relations between the topologies on $L^\infty$ associated with the duality $\langle L^1, L^\infty\rangle$ and its order topology.

math.FA