From my reading, $\mathrm{SU}(4)$ has 15 parameters and $\mathrm{SU}(2)$ has 3 paramaters that range differently with certain parameter (rotation angle). And all the parameter is linearly independent to each other.
My question are:
- What the characteristic of each of the parameter?
- If I choose two of them, what is the reason behind the theory?
- Can anyone explain to me or suggest any book/paper to me to understand the parameter itself.