# What is matrix norm in (Collins, 2001)

I am studying "A generalization of PCA to the exponential family" (Collins et al., 2001) and I don't understand some notations.

What is the meaning of the matrix squared norm on page 6 ? Is it a frobenius norm?

If it's a matrix... what does matrix quotient (division) mean ?

If it's a scalar, is it equivalent to the following notation ?

$$A^{(t)}=\frac{1}{\left \|\mathbf{V}^{(t-1)} \right \|^2}\mathbf{X}(\mathbf{V}^{(t-1)})^T$$

While $$V$$ is dimension $$l \times d$$, in that section Collins et. al. write, "First, we concentrate on the simplest case where there is just a single component so that $$l = 1$$." That makes $$V$$ just a vector and $$\|V\|$$ the regular 2-norm for vectors.