I am aware that the unit vector type has some potential limitations in practice, nonetheless I would like to try it just to gauge some hypothesis I have. From the documentation thought it is unclear what type of prior I am allowed to specify for it. I haven’t understood if Stan defines a standard prior for it, and hence we should not define it by ourselves, or if wee can define any prior we want and then STAN will try to deal with the normalization under the hood.

An example would be to understand if such a specification makes sense:

```
......
parameters {
unit_vector[N] nu_norm[K];
}
....
model{
for (k in 1:K){
target += normal_lpdf(nu_norm[k]| 0, sigmap);
.....
}
```