As far as I understand, Calabi ansatz is (in particular) a way to produce KahlerKähler metrics on total spaces of line bundles (or their disk subbudles) over KahlerKähler manifolds of the following form:
Calabi Ansatz. Let $p:(L,h)\to (M,\omega_M)$ be a Hermitian line bundle over a KahlerKähler manifold $M$. Consider on the total space $L$ the following two-form:
$$\omega_L=p^*(\omega_M)+dd^cf(t).$$
Here $t=t(v)=\log|v|_h$$t=t(v)=\log\lvert v\rvert_h$ is the log of the norm function on $L$ defined by $h$ and $f\in C^{\infty}(\mathbb R^1)$.
Question. As far as I understand, $\omega_L$ is KahlerKähler on some disk sub-bundle of the total space $L$ provided $f$ satisfies certain (convexity?) conditions. Are you aware of a good reference on this that would give these conditions on $f$? (I am aware of a few articles, like Hwang-SingerHwang–Singer (TransactionA momentum construction for circle-invariant Kähler metrics, Transactions of the AMS 2002), but would like something addressing my question more directly.)