On the exactness of the conditions of embedding theorems for spaces of functions with mixed logarithmic smoothness

The article considers the Lorentz space $L_{p,\tau }({\mathbb{T}}^m)$, $2\pi$ of periodic functions of many variables and $S_{p,\tau ,\theta }^{0,\bar{b}}\mathbf{B}$, $S_{p,\tau ,\theta }^{0,\bar{b}}B$ – spaces of functions with mixed logarithmic smoothness. The article establishes necessary and sufficient conditions for embedding the spaces $S_{p,\tau ,\theta }^{0,\bar{b}}\mathbf{B}$ and $S_{p,\tau ,\theta }^{0,\bar{b}}B$ into each other.