Scale/Resize a single letter in mathmode with its subscript/superscript unchanged

Question

Is there a way to do this? Currently I am using something like the following to do the job on scaling of a single letter in an equation:

\[
\int_{\Omega} (u - \text{\Large $\Pi_{\Omega}$} u) v \, dx = 0
\]

or

\[
\int_{\Omega} (u - \text{\scalebox{1.5}{$\Pi_{\Omega}$}} u) v \, dx = 0
\]

and as you can see, the \Omega in the subscript of \Pi is obviously bigger than the \Omega as the domain of the integral sign:

I am curious if there is a way to manually adjust the size of the sub/sup-script of this resized letter? I tried using \scriptsize and \scriptstyle, both seem not working in mathmode? or is there another solution for the rescaling/resizing other than exploiting \text{} or \scalebox{}[]{}. Thanks in advance!

Answer 1

The "large Pi" symbol you're looking for is called \prod (the analog of \sum for products)

\[
\int_{\Omega} (u - \prod\nolimits_{\Omega} u) v \, dx = 0
\]

The \nolimits is to avoid the subscript to go below the symbol in display style.

If you need a smaller symbol in display style, you can define

\newcommand{\sprod}{\mathop{\mathchoice
  {\textstyle\prod}
  {\prod}
  {\prod}
  {\prod}
}\nolimits}

and the result of

\[
\int_{\Omega} (u - \sprod_{\Omega} u) v \, dx = 0
\]

would be as follows