The Boutet de Monvel operators in variable Hölder–Zygmund spaces on $\mathbb{R}^{n}_+$

We consider Green operators from the Boutet de Monvel algebra in the Hölder–Zygmund spaces of variable smoothness on $\overline{\mathbb R}^{n}_+$. The order of smoothness depends on a point in the domain and may take negative values. The sufficient conditions of boundedness of the Boutet de Monvel operators are obtained.

ON THE HARMONIC ZYGMUND SPACES

In this paper we study a class ${\mathcal{Z}}_{H}$ of harmonic mappings on the open unit disk $\mathbb{D}$ in the complex plane that is an extension of the classical (analytic) Zygmund space. We extend to the elements of this class a characterisation that is valid in the analytic case. We also provide a similar result for a closed separable subspace of ${\mathcal{Z}}_{H}$ which we call the little harmonic Zygmund space.

Nikol’skii–Type Inequalities for Trigonometric Polynomials for Lorentz–Zygmund Spaces

Nikol’skii–type inequalities, that is inequalities between different metrics of trigonometric polynomials on the torus Td for the Lorentz–Zygmund spaces, are obtained. The results of previous paper “Nikol’skii inequalities for Lorentz–Zygmund spaces” are extended. Applications to approximation spaces in Lorentz–Zygmund spaces and to Besov spaces are given.