2

I'd like to input a long equation, so I had to cut it into two lines. But, there's a couple of {} at the start of the first line of the equation and the end of the second line of the equation, and the 'equal height brackets' doesn't support \\ in it. I've used the \qty{} command of the package physics, or the \ab\{\} command of the package physics2, just like the code below:

\documentclass[9pt,a4paper]{article}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{extarrows}
\usepackage{fixdif,physics2}
\def\e{\mathrm{e}}
\usephysicsmodule{ab,ab.legacy,braket,nabla.legacy}
\def\Re{\mathrm{Re}}
\begin{document}
\begin{equation}
    \begin{aligned}
        J_L(t)&=\frac{2e}{\hbar}\Re\ab\{\sum_{k,\alpha\in L}{V_{k\alpha,n(t)}G_{n,k\alpha}^<(t,t)}\}\\
        &\xlongequal{\sum_{n}\sum_m=\sum_{n,m}}\frac{2e}{\hbar}\Re\ab\{\sum_{\substack{k,\alpha\in L\\n,m}}V_{k\alpha,n}(t)\int_{-\infty}^t\d t_1V_{k\alpha,m}^*\ab(t_1)\times\ab[G_{nm}^r\ab(t,t_1)\times\ab(\i f\ab(\epsilon_{k\alpha}^0)\exp\ab[-\i\int_{t}^{t_1}{\d t_2\epsilon_{k\alpha}(t_2)}])\\
        &\ \ +G_{nm}^<\ab(t,t_1)\times\ab(\i\theta\ab(-t_1+t)\exp\ab[-\i\int_{t}^{t_1}{\d t_2\epsilon_{k\alpha}(t_2)}])\vphantom{\int_t^{t_1}}]\}\\
      \end{aligned}
\end{equation}
\end{document}

they all returned me errors:

Extra }, or forgotten \right.
<template> }
Missing } inserted.
<inserted text> 

Then, I used the command \left\{ at the at the start of the first line of the equation and \right\} at the end of the second line of the equation, however it also returned me the errors above.

Then, I used the command \left\{ at the start of the first line and \right. at the end of the first line, used the command \left. at the start of the second line and \right\} at the end of the second line, the errors disappeared, however, the height of the right bracket } doesn't equal to the height of the left bracket {. enter image description here

The code is just like below:

\documentclass[9pt,a4paper]{article}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{extarrows}
\usepackage{fixdif,physics2}
\def\e{\mathrm{e}}
\usephysicsmodule{ab,ab.legacy,braket,nabla.legacy}
\def\Re{\mathrm{Re}}
\begin{document}
\begin{equation}
    \begin{aligned}
        J_L(t)&=\frac{2e}{\hbar}\Re\ab\{\sum_{k,\alpha\in L}{V_{k\alpha,n(t)}G_{n,k\alpha}^<(t,t)}\}\\
        &\xlongequal{\sum_{n}\sum_m=\sum_{n,m}}\frac{2e}{\hbar}\Re\left\{\sum_{\substack{k,\alpha\in L\\n,m}}V_{k\alpha,n}(t)\int_{-\infty}^t\d t_1V_{k\alpha,m}^*\ab(t_1)\times\left[G_{nm}^r\ab(t,t_1)\times\ab(\i f\ab(\epsilon_{k\alpha}^0)\exp\ab[-\i\int_{t}^{t_1}{\d t_2\epsilon_{k\alpha}(t_2)}])\right.\right.\\
        &\ \ \left.\left.+G_{nm}^<\ab(t,t_1)\times\ab(\i\theta\ab(-t_1+t)\exp\ab[-\i\int_{t}^{t_1}{\d t_2\epsilon_{k\alpha}(t_2)}])\vphantom{\int_t^{t_1}}\right]\right\}\\
      \end{aligned}
\end{equation}
\end{document}

Finally, I found that I can add a 'virtual' height of the first line, is just add the command \vphantom{\sum_{\substack{k,\alpha\in L\\n,m}}} before the \right\} at the end of the second line, just like the code below:

\documentclass[9pt,a4paper]{article}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{extarrows}
\usepackage{fixdif,physics2}
\def\e{\mathrm{e}}
\usephysicsmodule{ab,ab.legacy,braket,nabla.legacy}
\def\Re{\mathrm{Re}}
\begin{document}
\begin{equation}
    \begin{aligned}
        J_L(t)&=\frac{2e}{\hbar}\Re\ab\{\sum_{k,\alpha\in L}{V_{k\alpha,n(t)}G_{n,k\alpha}^<(t,t)}\}\\
        &\xlongequal{\sum_{n}\sum_m=\sum_{n,m}}\frac{2e}{\hbar}\Re\left\{\sum_{\substack{k,\alpha\in L\\n,m}}V_{k\alpha,n}(t)\int_{-\infty}^t\d t_1V_{k\alpha,m}^*\ab(t_1)\times\left[G_{nm}^r\ab(t,t_1)\times\ab(\i f\ab(\epsilon_{k\alpha}^0)\exp\ab[-\i\int_{t}^{t_1}{\d t_2\epsilon_{k\alpha}(t_2)}])\right.\right.\\
        &\ \ \left.\left.+G_{nm}^<\ab(t,t_1)\times\ab(\i\theta\ab(-t_1+t)\exp\ab[-\i\int_{t}^{t_1}{\d t_2\epsilon_{k\alpha}(t_2)}])\vphantom{\int_t^{t_1}}\right]\vphantom{\sum_{\substack{k,\alpha\in L\\n,m}}}\right\}\\
      \end{aligned}
\end{equation}
\end{document}

The question is 'solved', this is the effect that I want: enter image description here

However, this is too much trouble... I'd like to know if there's a simple command just like the command \qty of package physics or \ab of package physics2 can achieve the effect I want?

3
  • 1
    I think you need to use \Bigl and \Bigr or maybe \biggl and \biggr or whatever size fits you here.
    – mickep
    Nov 7, 2023 at 8:55
  • See tex.stackexchange.com/a/21291/82917
    – campa
    Nov 7, 2023 at 8:55
  • Aside: The article document class doesn't recognize (and thus ignores) the option 9pt.
    – Mico
    Nov 7, 2023 at 9:08

1 Answer 1

4

Rather than define and use various \vphantom contstructs, do learn how to use \Bigg[lr] and \bigg[lr]. Incidentally, your formula needs to be spread across four rows, not just three, in order for it not to protrude into the margins. Oh, and don't use \def unless you are willing to take the risk of clobbering pre-existing macros; the macro \Re is a case in point.

enter image description here

\documentclass[%9pt, % "9pt" is not a recognized option
               a4paper]{article}
\usepackage{geometry}
\usepackage{mathtools} % for "\smashoperator" macro
\usepackage{extarrows,fixdif}
\let\Re\relax % first, undefine the existing '\Re' macro
\DeclareMathOperator\Re{\mathrm{Re}} % next, redefine '\Re'
%\def\e{\mathrm{e}} % not needed 
\providecommand\I{\mathrm{i}} % imag. unit. Use only in math mode

\begin{document}

\begin{equation}
\begin{aligned}[b]
J_L(t)
  &=\frac{2e}{\hbar} \Re\Biggl\{ \,
    \smashoperator[r]{\sum_{k,\alpha\in L}}
    V_{k\alpha,n(t)}G_{n,k\alpha}^<(t,t)\Biggr\}\\
  &\xlongequal{\sum_{n}\sum_m=\sum_{n,m}}
    \frac{2e}{\hbar} \Re\Biggl\{ \,
    \smashoperator[r]{\sum_{\substack{k,\alpha\in L\\n,m}}}
    V_{k\alpha,n}(t)
    \int_{-\infty}^t \d t_1 V_{k\alpha,m}^* (t_1)\\
  &\quad
    \times\Biggl[G_{nm}^r(t,t_1)\times
    \biggl(\I f(\epsilon_{k\alpha}^0)
    \exp\biggl[-\I\int_{t}^{t_1} \d t_2\epsilon_{k\alpha}(t_2) 
    \biggr]\biggr) \\
  &\qquad
    +G_{nm}^< (t,t_1)\times\biggl(\I\theta(-t_1+t)
    \exp\biggl[-\I\int_{t}^{t_1} \d t_2\epsilon_{k\alpha}(t_2)
    \biggr]\biggr)
    \Biggr]\Biggr\}
\end{aligned}
\end{equation}
\end{document}
8
  • 1
    \i throws warning in math mode. I'd suggest soething along the lines of \newcommand*{\I}{\text{\i}}, then one can redefine the imaginary unit (I think that's what it's supposed to be) as needed.
    – campa
    Nov 7, 2023 at 10:15
  • @campa - Good point. Let me fix this right away.
    – Mico
    Nov 7, 2023 at 10:17
  • Actually, thinking about it \textup might be better. You don't want that to be italic in a theorem environment.
    – campa
    Nov 7, 2023 at 10:23
  • @campa - I ended up using \mathrm{i}. :-)
    – Mico
    Nov 7, 2023 at 10:24
  • 1
    @Axia - What do you mean? First off, in your code, many of the \ab instructions have no effect at all; I wouldn't call that an example of "fine control". Second, the only time that \bigg and \Bigg fall short is if what's needed is tall delimiters bigger than \Bigg. However, that's not the case here.
    – Mico
    Nov 7, 2023 at 10:58

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