Suppose we have a hermitian matrix $H(t)$ continuously depend on parameter $t$, it's easy to know that the eigenvalue $\lambda_i(t)$ of it is continuous$^1$, but what about eigenvectors of it? Is there some theorem tells us that in what condition of $H(t)$, the continuous eigenvectors will be guaranteed?
This question is duplicated with this one while I think it will be better answered here.
1. See this question.