4

Just wondering if there's a particular way to do the following in LaTeX:

enter image description here

where I've equated a particular part of the main equation to a little equation, given by T and U.

Thanks in advance!

9
  • 1
    Welcome! amsmath provides \underbrace, with usage \underbrace{a^2+b^2+c^2}_{=T}.
    – 1010011010
    Commented May 8, 2015 at 13:03
  • 2
    Related: vertical equal sign Commented May 8, 2015 at 13:05
  • Schrödinger's equation ;-) .. The ^ above the potential operator is out of alignment. It should be over U only
    – user31729
    Commented May 8, 2015 at 13:06
  • @1010011010, thank you, that is exactly what I was looking for! You should post that as an answer. Commented May 8, 2015 at 13:13
  • 1
    @HarrySmith: For the typesetting of the kets you might have a look on the braket package
    – user31729
    Commented May 8, 2015 at 13:15

3 Answers 3

1

This should get you going. I've introduced a few commands to make it easier to typeset some parts of the equations in a more automated way, or if you wish to change something all over the document at once. *They're not strictly necessary for the obtained result.

http://i.imgur.com/70hSYbF.png?1

\documentclass{article}
\usepackage{amsmath,mathtools}
\newcommand\partt[1][]{%
  \ifmmode
    \frac{\partial#1\mathstrut}{\partial t}%
  \fi
}
\newcommand\ChristianHupfer[1]{%
  \ifmmode
    \lvert
      #1%
    \rangle
  \fi
}
\newcommand\rotateequal[1]{%
  \ifmmode
    \underset{#1}{\rotatebox{90}{$=$}}%
  \fi
}
\newcommand\myvector[1]{%
  \ifmmode
    \mathbf#1%
  \fi
}
\newcommand\largemathstrut{%
  \ifmmode
    \frac{\mathstrut}{\mathstrut}
  \fi
}
\begin{document}
\[
i\hbar\partt\ChristianHupfer{\psi(\myvector{r},t)} 
= 
\underbrace{\frac{-\hbar^{2}}{2m}\nabla^2\largemathstrut}_{\rotateequal{T}}\ChristianHupfer{\psi(\myvector{r},t)}
+
\underbrace{\hat{U(\myvector{r})}\largemathstrut}_{\rotateequal{U}}\ChristianHupfer{\psi(\myvector{r},t)}
\]
\end{document}
4
  • \waveleft? ;-) That's a ket state vector
    – user31729
    Commented May 8, 2015 at 13:26
  • @ChristianHupfer Fixed. :-)
    – 1010011010
    Commented May 8, 2015 at 13:31
  • This is a very nice solution. It's a shame the standard \underbrace curly brace symbol is so ugly! Commented May 8, 2015 at 13:45
  • 1
    What's the purpose of \ifmmode in all those definitions? If you use those commands in a wrong place you'll get nothing, instead of a clear error message (Missing $ inserted)
    – egreg
    Commented May 8, 2015 at 15:11
3

Here, I provide \undereq{} to be used in the \underbrace subscript.

\documentclass{article}
\usepackage{amsmath,stackengine,graphicx}
\stackMath
\newcommand\undereq[1]{%
  \stackunder[2pt]{\mkern1mu\rotatebox{90}%
                  {$\scriptstyle=\mkern-3mu$}}{\scriptstyle \mathstrut#1}%
}
\begin{document}
\[
  = \underbrace{\frac{-\hbar^2}{2m}\nabla^2}_{\undereq{T}}\lvert \psi(\mathbf{r},t)...
\]\end{document}

enter image description here

6
  • Although this provides the right formatting for equations, the main body text now overlaps my headers. Is there a way to fix this? Commented May 8, 2015 at 13:29
  • @HarrySmith I'm not sure I understand. When you say "headers," do you mean the stuff at the top of the page? If so, I don't see how this particular implementation could produce that effect. Commented May 8, 2015 at 13:30
  • I am writing using the book class, with the fancyhdr package. It results in this: 1drv.ms/1GToe1a. Commented May 8, 2015 at 13:34
  • @HarrySmith That web site is blocked to me, so I cannot see it. However, using book class, fancyhdr package, with a \pagestyle{fancy} and a \fancyhead{This is a test} does not produce any interference with the header using my MWE. Commented May 8, 2015 at 13:40
  • Hosting shared files on OneDrive is less-than-ideal, haha. This one may work: 1drv.ms/1H3EwqP. However, I tried this solution in a regular document and it worked very nicely -- and the curly brace looks nice, too. I may use this in future documents. Thank you! Commented May 8, 2015 at 13:48
1

A possible better way to set your equation:

\documentclass{article}
\usepackage{amsmath,mathtools}
\usepackage{braket,graphicx}

\newcommand\pder[2][]{%
  \frac{\partial#1\mathstrut}{\partial #2}%
}

\newcommand\roteq{\mathpalette\doroteq\relax}
\newcommand\doroteq[2]{%
  \rotatebox[origin=c]{90}{$#1=$}%
}

\renewcommand\vec[1]{\mathbf{#1}}

\begin{document}

\[
\newcommand{\BF}{\vphantom{\frac{-\hbar^{2}}{2m}\nabla^2}} % just for this equation
i\hbar\pder{t}\ket{\psi(\vec{r},t)} 
= 
\underbrace{\frac{-\hbar^{2}}{2m}\nabla^2}_{\substack{\roteq\\T}}\ket{\psi(\vec{r},t)}
+
\underbrace{\BF\widehat{U(\vec{r})}}_{\substack{\roteq\\U}}\ket{\psi(\vec{r},t)}
\]

\end{document}

enter image description here

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