如何使垂直线后的 x 和 y 具有与 \partial 中的小 \psi 和 x 相同的大小

Question

\begin{equation*}
\psi(\omega) = \left.{\psi}\right|_{\omega=0} +
 \omega \cdot 
 \underbrace {\left.\dfrac{d\psi}{d\omega}\right|_{\omega=0} }_{\left.\frac{\partial \psi}{\partial x}\right|_{\substack{{x =0} \\ {y=0}}}} \,+ \,\dfrac{\omega^2}{2} \,\cdot\, \underbrace {\left.\dfrac{d^2\psi}{d\omega \, d\omega}\right|_{\substack{\omega=0}}}_{\left.\frac{\partial \psi^2}{\partial x \partial x}\right|_{\substack{x=0 \\ y=0 }}} + \ldots +
   \dfrac{\omega^p}{p!} \cdot \dfrac{d^p\psi}{d\omega \cdot \ldots \cdot d\omega}
\end{equation*}

Answer 1

\substack我不会将这些指令的论点简化，而是增加相关分数表达式的大小，通过使用\tfrac而不是\frac。

\documentclass{article}
\usepackage{amsmath,xcolor}

\begin{document}

\textcolor{red}{Before}
\begin{equation*}
\psi(\omega) = \left.{\psi}\right|_{\omega=0} +
 \omega \cdot 
 \underbrace {\left.\dfrac{d\psi}{d\omega}\right|_{\omega=0} }_{\left.\frac{\partial \psi}{\partial x}\right|_{\substack{{x =0} \\ {y=0}}}} \,+ \,\dfrac{\omega^2}{2} \,\cdot\, \underbrace {\left.\dfrac{d^2\psi}{d\omega \, d\omega}\right|_{\substack{\omega=0}}}_{\left.\frac{\partial \psi^2}{\partial x \partial x}\right|_{\substack{x=0 \\ y=0 }}} + \ldots +
   \dfrac{\omega^p}{p!} \cdot \dfrac{d^p\psi}{d\omega \cdot \ldots \cdot d\omega}
\end{equation*}

\medskip
\textcolor{red}{After}
\begin{equation*}
\psi(\omega) = \psi\bigr|_{\omega=0} +
 \omega \cdot 
  {\underbrace {\frac{d\psi}{d\omega}\biggr|_{\omega=0} }%
 _{\tfrac{\partial\psi}{\partial x}\Bigr|_{\substack{x =0\\y=0 }}}} 
+
\frac{\omega^2}{2} \cdot 
  {\underbrace{\frac{d^2\psi}{d\omega\,d\omega}\biggr|_{\omega=0}}%
 _{\tfrac{\partial^2\psi}{\partial x\,\partial x}\Bigr|_{\substack{x=0 \\ y=0 }}}} 
+ \dots +
\frac{\omega^p}{p!} \cdot 
\frac{d^p\psi}{d\omega \ldots d\omega}
\end{equation*}
\end{document}

Answer 2

LaTeX 使用 4 种数学样式：\displaystyle、\textstyle和。最小的\scriptstyle是。\scriptscriptstyle\scriptscriptstyle

\substack，就像subarray环境使用一样\scriptstyle。作为一种解决方法，强制\scriptscriptstyle内部：

\substack{\scriptscriptstyle x =0 \\ \scriptscriptstyle y=0}