What is it about?

This article introduces a new class of function spaces called generalised Hajasz-Besov spaces, defined on metric measure spaces with the doubling and reverse doubling properties (RD-spaces). The work extends classical results for Besov spaces by combining two important ideas: using slowly varying functions to modify smoothness and replacing the basis space with rearrangement invariant spaces. The paper proves several embedding theorems, Sobolev-type embeddings, and results on essential continuity and Morrey-type embeddings for these new spaces, showing their relevance in both abstract and Euclidean settings.

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Why is it important?

Generalised Hajasz-Besov spaces provide a unified and more flexible framework for studying function spaces on metric measure spaces. This allows for finer control over the smoothness and integrability properties of functions, which is crucial for applications in partial differential equations, variational problems, and harmonic analysis. The embedding and continuity results obtained in the paper are essential for understanding the structure and regularity of solutions in these generalized contexts, making the work significant for both theoretical and applied mathematics.

Perspectives

On a personal level, this project has also been a great experience of collaboration with Joaquim Martín. Many of the key ideas emerged from long discussions, drawing diagrams, and testing examples until the theory started to fit together naturally. Looking ahead, I am excited about the possibilities this framework opens for further work, especially in connecting abstract functional analysis with concrete problems in engineering and applied sciences.

Walter Andrés Ortíz Vargas
Universidad Internacional de La Rioja

Read the Original

This page is a summary of: Generalised Hajłasz–Besov spaces on RD-spaces, Journal of Mathematical Analysis and Applications, March 2026, Elsevier,
DOI: 10.1016/j.jmaa.2025.130028.
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