Hi everyone, does someone have an idea to describe the class of functions $\Psi(z)$ satisfying
$$\Psi\in\mathcal{C}^2: z\in\mathbb{R}\rightarrow\Psi(z)\in\mathbb{R}_+$$
$$1-\frac{z\Psi'(z)}{\Psi(z)}+8s\Psi''(z)\geq 0$$
and
$$\Psi(0)=1$$
where $s$ is a given positive constant.
Many thanks! (A subset of this class is ok)
