Different spacing of only superscript vs superscript and subscript + mathrm vs operatorname

Question

I'd like to have superscript terms (gt) on the same line in the whole equation, but after I write the equation:

$\mathbf{T}^{\mathrm gt}=\{\mathbf{T}^{\mathrm gt}_1,\mathbf{T}^{\mathrm gt}_2,\ldots,\mathbf{T}^{\operatorname{gt}}_k\}$

I receive this:

I know I can add _{\phantom{1}} term, but it is not elegant as for equations without subscripts - I would have to add this phantom to be consistent in a whole document. Also is there a need to use operatorname or simple mathrm is enough?

Answer 1

You might use subdepth. But I don't recommend it.

\documentclass{article}
\usepackage{amsmath}
\usepackage{subdepth}
\newcommand{\gt}{\mathrm{gt}}
\begin{document}
[
%%% the following two lines are just to show the alignment
\sbox0{$\displaystyle\mathbf{T}^{\gt}$}
\rlap{\vrule height \dimeval{\ht0+0.1pt} depth -\ht0 width 4cm}
%%%
\mathbf{T}^{\gt}=
  {\mathbf{T}^{\gt}_1,\mathbf{T}^{\gt}_2,\ldots,\mathbf{T}^{\gt}_k}
]
\begin{center}
$%%% the following two lines are just to show the alignment
\sbox0{$\displaystyle\mathbf{T}^{\gt}$}
\rlap{\vrule height \dimeval{\ht0+0.1pt} depth -\ht0 width 4cm}
%%%
\mathbf{T}^{\gt}=
  {\mathbf{T}^{\gt}_1,\mathbf{T}^{\gt}_2,\ldots,\mathbf{T}^{\gt}_k}
$\end{center}
\end{document}

Note that \mathrm gt is wrong under any respect. Also \operatorname isn't good in that context.

---

If you have just a couple of these constructs, it's easier to add a few \vphantom.

For several instances of the same structure,

\documentclass{article}
\usepackage{amsmath}
\ExplSyntaxOn
\NewDocumentCommand{\tuple}{mm}
 {% #1 is the base symbol, #2 is the list of subscripts
  #1\sb{\vphantom{#2}} = {
  \seq_clear:N \l_tmpa_seq
  \clist_map_inline:nn { #2 }
   {
    \str_if_eq:nnTF { ##1 } { \dots }
     {
      \seq_put_right:Nn \l_tmpa_seq { \dotsc }
     }
     {
      \seq_put_right:Nn \l_tmpa_seq { #1\sb{##1\vphantom{#2}} }
     }
   }
  \seq_use:Nn \l_tmpa_seq { , }
  }
 }
\newcommand{\gt}{\mathrm{gt}}
\begin{document}
[
\tuple{\mathbf{T}^{\gt}}{1,2,\dots,k}
]
\begin{center}
$\tuple{\mathbf{T}^{\gt}}{1,2,\dots,k}$
\end{center}
[
\tuple{A}{1,2,3} \quad \tuple{B}{1,2,3,\dots}
]
\end{document}

Answer 2

I think that this code is between the good solutions:

\documentclass[12pt]{article}
\usepackage{amsmath, amssymb}
\begin{document}
$\mathbf{T}^{\substack{\mathrm{gt}}}{\phantom{\substack{1}}}={\mathbf{T}^{\substack{\mathrm{gt}}}{\substack{1}},\mathbf{T}^{\substack{\mathrm{gt}}}{\substack{2}},\ldots,\mathbf{T}^{\substack{\mathrm{gt}}}{\substack{k}}}$
\end{document}