The outer product

\begin{equation*} M = \vec{u} \otimes \vec{v} \end{equation*}

of two vectors

• \(\vec{u} \in \mathbb{R}^{m}\)
• \(\vec{v} \in \mathbb{R}^{n}\)

is a matrix \(M \in \mathbb{R}^{m \times n}\).