Suppose $G$ is a Lie group, $\mathcal{g}$ \mathfrak{g}$ its Lie algebra, if we have a smooth representation $(\pi,V)$, then it induces a an action of $\mathcal{g}$ \mathfrak{g}$ on $V$. Now conversely, if we have a nice (with properties you may assume) action of $\mathcal{g}$ \mathfrak{g}$ on $V$, can we say such action arises from some unique smooth action of $G$?
Here we may assume $G$ to be simply connected if needed. Thank you.

