On the Helmholtz decomposition in Morrey and block spaces

In this work, we obtain the Helmholtz decomposition for vector fields in Morrey, Zorko, and block spaces over bounded or exterior $C^1$ domains. Generally speaking, our proofs rely on a careful interplay of localization, flattening, and duality arguments. To accomplish this, we need to extend some classical tools in analysis and PDE theory to those spaces, including Stein extensions, compact embeddings, Poincaré inequalities, Bogovskii-type theorem, among other ingredients. Some of these findings may be of independent interest and applied to the study of a number of PDEs.