Prove or disprove: there is an analytic function $f$ on $D=\{z:~|z|<1\}$ such that $|f(z)|=e^{|z|},~z\in D.$
Attempt. I believe that such a function does not exist (besides, a candidate function would be for example $e^z$, but $|e^z|=e^{Rez}\leq e^{|z|}$, although I can not provide a proof of my claim.
Thanks in advance!
As $|f|\geq 1$ on $\mathbb{D}$, we can consider the analytic function $g=\dfrac{1}{f}$ on $\mathbb{D}$. Clearly $g \leq 1$ on $\mathbb{D}$, and $g(0)=1$. By Maximum Modulus Principle, $g$ and therefore $f$ is constant.