Let the following matrix given by
$\mathbf{Q} = \begin{bmatrix} \mathbf{u}_1^\intercal \mathbf{V}_1 \\ \vdots \\ \mathbf{u}_p^\intercal \mathbf{V}_p \end{bmatrix}$, $\mathbf{u}_i \in \mathbb{R}^{\delta_i}$, $\mathbf{V}_i \in \mathbb{R}^{\delta_i \times n}$, $\delta_i \in \mathbb{N}^+_*$, $i = 1, \cdots, p$.
Is there a way to write it in a more compact matricial form? If it gets "complicated" (ill-defined term, show the form and let me decide), make me aware.
I thank you sincerely.
