$K-$frames for Super Hilbert Spaces
Najib Khachiaa
TL;DR
This work studies how $K$-frames for $H_1$ and $L$-frames for $H_2$ relate to $K\oplus L$-frames for the super Hilbert space $H_1\oplus H_2$, and investigates $K\oplus L$-minimal frames and $K\oplus L$-orthonormal bases. By analyzing synthesis/analysis/frame operators and projecting onto components, the authors establish that a $K\oplus L$-frame on the direct sum implies component $K$- and $L$-frames, and they derive exact operator decompositions and duality relations across the direct sum. They further provide necessary and sufficient conditions for $K\oplus L$-minimal frames, and elucidate when $K\oplus L$-orthonormal bases can arise, including the roles of (co-)isometries and subspace orthogonality. The results yield a structured framework for multicomponent frame theory in super Hilbert spaces, with implications for joint reconstruction under componentwise operator constraints.
Abstract
Let $H_1$ and $H_2$ be two Hilbert spaces, $K$ and $L$ be bounded operatrors on $H_1$ and $H_2$ respectively. In this paper we study the relationship between $K$-frames for $H_1$ and $L$-frames for $H_2$ and $K\oplus L$-frames for $H_1\oplus H_2$. The $K\oplus L$-minimal frames and $K\oplus L$-orthonormal bases for $H_1\oplus H_2$ are also studied.
