How can we write \mathcal{a letter} as a subscript

Question

I wish to write T in the subscript of \rho as

\rho_{\raisebox{-2pt}{\tiny T}}

But the desired case is: writing the T in the format of \mathcal. When I write

\rho_{\raisebox{-2pt}{\tiny \mathcal{T}}}

TeXStudio does not render it in a correct way!

How can I reach this goal?

Answer 1

The argument of \raisebox is considered text mode, you have to put $ $ around \mathcal{T}

\documentclass{article}
\usepackage{amsmath}

\begin{document}
   $\rho_{\raisebox{-2pt}{\tiny $\mathcal{T}$}}$
\end{document}

Answer 2

i wonder why you not use simple

\documentclass[margin=3mm]{standalone}
%\usepackage[low-sup]{subdepth}

\begin{document}
 text  $\rho_{\mathcal{T}}$, text $\rho_{\mathcal{T}}^{}$
\end{document}

is something wrong with this?

according to rules how to set indices, i don't see what is wrong with this standard way of writing them.