Vortex and the Gradient of Divergence in Sobolev Spaces

Abstract

The properties of the vortex and the gradient of divergence operators ( $ \text{rot}$ and $\nabla \text{div}$ ) are studied in the space $ \mathbf {L}_2 (G) $ in a bounded domain $ G \subset \textrm {R}^3 $ with a smooth boundary $ \Gamma$ and in the Sobolev spaces: $ \mathbf{C}(2k, m)(G)\equiv \mathbf{A}^{2k}(G) \oplus \mathbf{W}^m(G)$. S.L. Sobolev studied boundary value problems for the scalar polyharmonic equation $\Delta^m\,u=\rho$ in the spaces $W_2^m(\Omega)$ with a generalized right-hand side and laid the foundation for the theory of these spaces. Its constructions have matrix analogs, here are some of them. Analogues of the spaces ${W}_2^{(m)}(G)$ in the classes $ \mathcal {A} $ and $ \mathcal {B} $ are the space $\mathbf{A}^{2k}(G)$ and $\mathbf{W}^m(G)$ of orders $ 2k> 0 $ and $ m> 0 $, and $ \mathbf {A}^{-2k} (G) $ and their dual spaces $ \mathbf{W}^{- m}(G) $. Pairs of spaces form a net of Sobolev spaces, its elements are classes $ \mathbf{C}(2k, m)(G)\equiv \mathbf{A}^{2k}(G) \oplus \mathbf{W}^m(G)$; the class $ \mathbf{C}(2k, 2k)$coincides with the Sobolev space $\mathbf{H}^{2k}(G)$. They belong to $\mathbf{L}_{2}(G)$, if $k\geq 0$ and $m\geq 0$. A wide field of problems has opened up: studying the operators $(\mathrm{rot})^p$, $ (\nabla \, \mathrm{div})^p$ for $ p = 1,2, ...,$ and others in the network Sobolev spaces.