How to place two line of text in front of the sum sign?

Question

So I have this \[ min\sum_{i=1}^{n} \] which results in

What should I change to get this:

Answer 1

Sorry for the short answer in advance. The \min command is already defined as a math operator and accepts arguments to be placed under. Notice the difference between the use in the text and the standalone equation use. (They are usually referred as inline math and displayed math)

\documentclass{article}
\begin{document}
Hi I want to use some numerical optimization method to solve the problem 
formulated by $\min_{S(t)} \sum_{i=1}^{n}$, but it looks terrible and my 
eyes hurt. So once again with much nicer,
\[
\min_{S(t)} \sum_{i=1}^{n}
\]
I still don't know what to sum up. That's some future work.
\end{document}

Answer 2

You can use the \underset command with package amsmath

\usepackage{amsmath}
\[ \underset{S(t)}{\min}\sum_{i=1}^{n} \]

Edit: As percusse noted, you can use \min_{S(t)}. You must load the amsmath package however for it to work.

\underset is more general and can support non-standard operators such as:

\[ \underset{S(t)}{\operatorname{arg~min}} \]