LaTeX Squeezes Notation in `\frac{}{}` Environment [duplicate]

Question

I have to write an expression of the form

\frac{1}{E_{s}^{x}}

However, the term is squeezed by TeX in the denominator (the x does not have the same height as if I did not use a fraction). Here the output:

How can the heights be made consistent?

Here is an MWE:

\documentclass{scrbook}

\begin{document}
    $$\frac{1}{E_{s}^{x}}$$ $$E_{s}^{x}$$
\end{document}

Thank you.

Answer 1

If a \frac expression is encountered while in \displaystyle math mode, the numerator term is typeset in (ordinary) \textstyle and the denominator is typeset in so-called "cramped" \textstyle. If you don't like this default behavior, you need to insert -- depending on the look you want to achieve -- either \displaystyle or \textstyle at the start of the denominator material.

\documentclass{scrbook}
\begin{document}
$\displaystyle E_{s}^{x} \quad 
 \textstyle    E_{s}^{x}$

\bigskip
$\displaystyle 
 \frac{1}{E_{s}^{x}} \quad 
 \frac{1}{\displaystyle E_{s}^{x}} \quad 
 \frac{1}{\textstyle    E_{s}^{x}}$
\end{document}