Elena & Fabrice's Web

\(\newcommand{\pt}{\partial_t}\)With MathJax, you can use \newcommand in enclosed $...$ characters to define a macro in any given page (e.g., \newcommand{\pt}{\partial_t} turns $\pt$ into $\pt$). If you want a popular macro to be defined once and for all, without having to include the definition each time, you have to declare it in a Config.js file. In the mediawiki extension version, the file is:

- mwMathJaxConfig.js

There's already a list of definitions. The syntax is not the most obvious as it needs to translates $\mathrm{\TeX}$ syntax into javascript. Macros I use all the times are:

```
\newcommand{\ud}[1]{{#1^{\dagger}}}
\newcommand{\bra}[1]{\left\langle #1\right|}
\newcommand{\ket}[1]{\left| #1\right\rangle}
\newcommand\Tr{\mathrm{Tr}}
```

And this needs be written:

```
bra: ['{\\left\\langle #1\\right|}',1],
ket: ['{\\left| #1\\right\\rangle}',1],
ud: ['{#1^{\\dagger}}',1],
Tr: '\\mathrm{Tr}'
```

This turns, e.g., $$\ud{a}\ket{n}=\sqrt{n+1}\ket{n+1}$$ into:

- $$\ud{a}\ket{n}=\sqrt{n+1}\ket{n+1}$$

There are good discussions on google groups:

- http://goo.gl/kyY9U
- https://groups.google.com/forum/?fromgroups#!topic/mathjax-users/PRsSESbpHzg - defines a 3-argument macro.