# Small written under inf

I need to obtain something like this:

but everything I try put the written under inf on the same line or write them in an enormous font. What can I do?

• (1) welcome, (2) as always here, please post a full minimal example so we can see what you are doing. (3) Assuming you are loading the amsmath package and that this is a displayed formula: \inf_{\substack{u_1,u_2: \\ u_1+u_2=u}} Jun 21 '18 at 13:35

As daleif suggested, \substack is the tool. However, the horizontal spacing can still be adjusted in various ways. I show the raw result, and then with a \mathclap and some \mkern.

\documentclass{article}
\usepackage{mathtools,newtxmath}
\begin{document}
$F(x,z,u) = \inf_{\substack{u_1,u_2: \\ u_1+u_2=u}} \bigl\{F_1(x,z,u_1) + F_2(x,z,u_2)\bigr\}$$F(x,z,u) = \mkern6mu\inf_{\mathclap{\substack{u_1,u_2: \\ u_1+u_2=u}}} \mkern6mu\bigl\{F_1(x,z,u_1) + F_2(x,z,u_2)\bigr\}$
\end{document}


If controlling the vertical spacing of the stack is essential, here is a tabstackengine solution. There is 4pt below the \inf and 2pt between the \scriptstyle items. By increasing the vertical gap below \inf, the horizontal \mkern can also be reduced.

\documentclass{article}
\usepackage{newtxmath}
\usepackage{tabstackengine}
\stackMath
\TABstackMath
\TABstackMathstyle{\scriptstyle}
\begin{document}
$\renewcommand\useanchorwidth{T} \setstackgap{S}{2pt} F(x,z,u) = \mkern3mu\stackunder[4pt]{\inf}{\tabbedShortstack{u_1,u_2: \\ u_1+u_2=u}} \mkern3mu\bigl\{F_1(x,z,u_1) + F_2(x,z,u_2)\bigr\}$
\end{document}


Another way to obtain a netter hirizontal spacing without having to set math kernin manually is to use the \smashoperator command:

\documentclass{article}
\usepackage{mathtools,newtxmath}

\begin{document}

$F(x,z,u) = \inf_{\substack{u_1,u_2: \\ u_1+u_2=u}} \bigl\{F_1(x,z,u_1) + F_2(x,z,u_2)\bigr\}$
$F(x,z,u) = \smashoperator{\inf_{\substack{u_1,u_2:\enspace \\ u_1+u_2=u}}} \bigl\{F_1(x,z,u_1) + F_2(x,z,u_2)\bigr\}$

\end{document}