provides the typesetting capability
to create virtually any mathematical expression you could ever want in a
paper. Unfortunately, you may find yourself typing long
strings of symbol commands over and over again.
For example,
representation theory people may find themselves
typing something like
$$\widehat{f}(\rho\uparrow_{_G}^H)$$
It would be nice if you could type a shorter string. You can do this by defining your own ``macro'' with a line like this
\newcommand{\fhatrhoinG}{\widehat{f}(\rho\uparrow_{_G}^H)}
\fhatrhoinG
\newtheorem
command, this line can appear anywhere in your file (before
the first use of the macro it defines), but it is
conventional to put it between the \documentstyle and
\begin{document} lines.
You can also define commands which take parameters. For example, suppose that H and G might vary in the above example. Then the following macro can be defined:
\newcommand{\fhatrhoin}[2]{\widehat{f}
(\rho\uparrow_{_{#1}}^{#2})}
[2] means that there are two arguments. The two
arguments are inserted in the macro's text where
{#1} and {#2} appear.
Thus, typing the command
$$\fhatrhoin{K}{\operatorname{Stab}(K)}$$
While you're at it, you could also define
\newcommand{\Stab}{\operatorname{Stab}}
if you have stabilizers in your document.