TITLE: Singular Value Decomposition of Rank 1 matrix
QUESTION [6 upvotes]: I am trying to understand singular value decomposition.  I get the general definition and how to solve for the singular values of form the SVD of a given matrix however, I came across the following problem and realized that I did not fully understand how SVD works:
Let $0\ne u\in \mathbb{R}^{m}$.
Determine an SVD for the matrix $uu^{*}$.
I understand that $uu^{*}$ has rank 1 and thus only has one singular value i.e. 
$$\Sigma =  \begin{pmatrix} 
  \sigma_1 & \ldots & 0\\
  0& \ldots & 0 
\end{pmatrix} 
\in\mathbb{R}^{m\times m}$$
and I realize since $uu^{*}\in\mathbb{R}^{m\times m}$ then for $uu^{*}=U\sum V^{*}$ that $U,\Sigma,V\in\mathbb{R}^{m\times m}$.  Additionally, I realize that the columns of $U$ and $V$ are orthonormal.
I guess my question is how do you determine U and V from $uu^{*}$?

REPLY [7 votes]: The short SVD of $uu^*$ is $v\sigma v^*$ with $v=\frac{u}{\|u\|}$ and $σ=\|u\|^2$.
If you compute the bisector $w=u+\frac{u_1+0}{|u_1|+0}\|u\|e_1$ of $u$ and $e_1$, then you can get a full unitary matrix $V$ as the reflection matrix $I-2\frac{ww^*}{\|w\|^2}$, so that $uu^*=V\Sigma V^*$