I would like to write a map between two objects, with a map below which specify where any single object is sent. To be more precise. I want to write
$A \rightarrow B$, and right below it
$\alpha \mapsto \beta$. I tried with the command
$\underset$ but the maps below gets too smaller, and it's not aligned to the map above. What is the right command?
I apologize if this question has been already asked. To me it looks elementary, nevertheless I couldn't find it nor here nor googling around. Thank you very much for your time!