Square-to-Cube Lindelöfness and Power Separations in Hattori Spaces

Abstract

Let \(H(A)\) be the Hattori space associated with \(A\subseteq\mathbb R\), and put \(B=\mathbb R\setminus A\). Kulesza announced at the 2018 Joint Mathematics Meetings that Lindelöfness of \(H(A)^{2n}\) forces Lindelöfness of \(H(A)^{2n+1}\) for every positive integer \(n\). The meeting abstract states this implication without a proof. This paper proves the case \(n=1\) in ZFC. The same one-sided geometry gives a pointwise half-space criterion for affine discreteness and, when \(H(A)^2\) is Lindelöf, a four-coordinate obstruction for uncountable closed discrete monotone traces. Known results on mixed Sorgenfrey--Euclidean products lead to hereditary-Lindelöf criteria for finite powers, a countable-power characterization, and a finite-power Lindelöf reduction. A transfinite construction gives \(A\subseteq\mathbb R\) for which \(H(A)^2\) and \(H(A)^3\) are Lindelöf, whereas \(H(A)^4\) contains a closed discrete affine line of cardinality \(\mathfrak c\).