Rearrangement Estimates and Limiting Embeddings for Anisotropic Besov Spaces

The paper is dedicated to the study of embeddings of the anisotropic Besov spaces \(B_{p,{\theta _1}, \ldots ,{\theta _n}}^{{\beta _1}, \ldots ,{\beta _n}}\) (ℝⁿ) into Lorentz spaces. We find the sharp asymptotic behaviour of embedding constants when some of the exponents β_k tend to 1 (β_k < 1). In particular, these results give an extension of the estimate proved by Bourgain, Brezis, and Mironescu for isotropic Besov spaces. Also, in the limit, we obtain a link with some known embeddings of anisotropic Lipschitz spaces.

One of the key results of the paper is an anisotropic type estimate of rearrangements in terms of partial moduli of continuity.