How do you put text below other text?

Question

I need to write the expression meaning optimize over the parameter set. I think I should write something like

$\arg \max_{\substack{w \\ \phi}} f(w,\phi)$

but this puts the subscript below at the right of \max and I'd like to put those subindexes below and centered on the max word.

Which command should I use?

Thanks in advance.

Answer 1

Have you tried display mode math instead of text mode math. That is, try either:

$\displaystyle\arg \max_{\substack{w \\ \phi}} f(w,\phi)$

Or try:

\[ \arg \max_{\substack{w \\ \phi}} f(w,\phi) \]

Answer 2

See: http://www.breakthru.altervista.org/?p=27

using

\underset{x}{\operatorname{argmax}}