Let $f\in C^2(\mathbb R)$ be positive and $g:=\ln f$. Assume $$g'=\frac{f'}f$$ is Lipschitz continuous and hence $g''$ is bounded.
Is $g'''$ bounded too?
Let $f\in C^2(\mathbb R)$ be positive and $g:=\ln f$. Assume $$g'=\frac{f'}f$$ is Lipschitz continuous and hence $g''$ is bounded.
Is $g'''$ bounded too?
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No, of course. Let $$u(x)=\begin{cases} e^{-x^2}x^2\sin x^{-2}&\text{if }x\ne 0\\ 0&\text{if }x=0\end{cases}$$ and consider $$f(x)=\exp\left(\int_0^x\,dt\int_0^t u(s)\,ds\right)$$
Then, $(\ln f)''=u$, which is bounded and continuous, but $$u'(x)=\begin{cases} 2(1-x^2)xe^{-x^2}\sin x^{-2}-\frac2xe^{-x^2}\cos x^{-2}&\text{if }x\ne 0\\ 0&\text{if }x=0\end{cases}$$ is unbounded.