Unwanted spaces between characters in math mode

Question

When typesetting $INDEX^{LOYALTY}$ in math mode, I realize that it creates a space in between Character Y and A. I just wonder if there is any way to remove this unwanted gap.

My code is as follows:

\documentclass[12pt]{article}
\usepackage[a4paper,left = 2.5 cm, right=2.5 cm, top = 2.5 cm, bottom = 2.5 cm]{geometry}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{setspace}
\usepackage{graphicx}
\usepackage{float}
\usepackage{bm}
\begin{document}
$INDEX^{LOYALTY}$
\end{document}

Thank you very much!!!

Answer 1

If you want to interpret the letters in INDEX and LOYALTY as words, not individual symbols, you can use \mathrm{} (Roman font in math mode.)

\documentclass[varwidth, preview]{standalone}

\usepackage[T1]{fontenc}

\begin{document}
\( \mathrm{INDEX}^\mathrm{LOYALTY} \)
\end{document}

This also works with unicode-math, which will set the words in your text font and has a separate \symup{} command for upright letters that are individual symbols, not words.

One way to get text-mode italic letters is with \mathit{} from unicode-math or amsfonts. This is what I recommend. You can also wrap arbitrary text-mode formatting inside \text{} from amsmath.

\documentclass[varwidth, preview]{standalone}

\usepackage{unicode-math}

\begin{document}
\( \mathit{INDEX}^{\mathit{LOYALTY}} \)
\end{document}