I have the following code:

$\mathcal{I}(A,B) = \inf_{\substack{h : M\times I\rightarrow M\\ h(\cdot,t) \;homeomorphism\\ h(x,0) = x\;\forall\; x\in X\\ h(A,1) = B }} \max_{x\in X} \text{len} \;h(x, \cdot)$


But the conditions in my substack are very tiny with respect to the rest of the equation.

Is there a way to increase the size of just the text in the substack? Maybe the spacing as well?

\substack is a modified array definition using smaller fonts so you can use a full array (as in the second example) but it's hard to read and I'd consider a different layout as in the third example where the condition is pulled out of the display. multi-letter identifiers such as homomorphism should never be set in math italic.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$\mathcal{I}(A,B) = \inf_{\substack{h : M\times I\rightarrow M\\ h(\cdot,t) \;\text{homeomorphism}\\ h(x,0) = x\;\forall\; x\in X\\ h(A,1) = B }} \max_{x\in X} \text{len} \;h(x, \cdot)$

$\mathcal{I}(A,B) = \inf_{\begin{array}{@{}c@{}}h : M\times I\rightarrow M\\ h(\cdot,t) \;\text{homeomorphism}\\ h(x,0) = x\;\forall\; x\in X\\ h(A,1) = B \end{array}} \max_{x\in X} \text{len} \;h(x, \cdot)$

$\mathcal{I}(A,B) = \inf_{h} \max_{x\in X} \text{len} \;h(x, \cdot)$
where $h$ satisfies:\\
$h : M\times I\rightarrow M$,
$h(\cdot,t) \;\text{homeomorphism}$,
$h(x,0) = x\;\forall\; x\in X$,
$h(A,1) = B$

\end{document}

• Thanks for the input! I ended up pulling the conditions out afterwards as you suggested. It's much more readable this way. (Before I was trying to define it as given in a paper I was citing). Apr 20, 2013 at 20:51