Geometric Properties of Variable Mixed Lebesgue-Sequence Spaces

Abstract

We investigate the geometric properties of the variable mixed Lebesgue sequence space \(\ell^{q(\cdot)}(L^{p(\cdot)})\). Assuming that \(q_->1\), \(p_+<\infty\), and \(q(\cdot)\le p(\cdot)\) almost everywhere, we prove that both \(\ell^{q(\cdot)}(L^{p(\cdot)})\) and its dual space are strictly convex and smooth. Moreover, we establish that \(\ell^{q(\cdot)}(L^{p(\cdot)})\) is uniformly convex under these assumptions. We further show that the condition \(q_->1\) is sharp: when \(q_-=1\), the space fails to be uniformly convex, and its modular is not uniformly convex either. Finally, we apply these geometric results to the renormability of the associated variable-exponent Besov space \(B_{p(\cdot),q(\cdot)}^{α(\cdot)}\).

arXiv commentRevised version. The abstract and introduction have been revised, and the presentation of the main results has been improved