# Unexpected behavior of SIGMA symbol in eulervm

Consider the following minimal example (which has to use amsmath):

\documentclass{article}
\usepackage{amsmath}
\usepackage{eulervm}
\begin{document}
\begin{align*}
\rm{text}  =
x_\sigma
\end{align*}
\end{document}


which yields the following:

.

Note the symbol which appears instead of the expected \sigma and the font used for x. By removing the eulervm package the result is as expected, namely:

.

Now, even more counterintuitive, if you comment out the first line in the align, namely \rm{text} = leaving the eulervm package in place I get:

.

Obviously, as shown in the last example, eulervm can typeset a \sigma symbol as a subscript, but not when there's some text in front...?

Can someone explain what is happening here?

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You are using improperly the obsolete command \rm: use \mathrm{text} instead. And never use \rm. –  egreg Jul 11 '12 at 9:09
@egreg: It is a code I got from a collaborator... Can you put it as an answer so I can accept it. –  Dror Jul 11 '12 at 9:12

## 1 Answer

Commands such as \rm or \bf have been obsolete since the release of LaTeX2e, almost twenty years ago.

They are declarations, so they should be placed inside braces:

{\rm text}


The \rm{text} form declares \rm for the whole formula, which explains why the x and the \sigma are typeset wrongly.

Nevertheless, as I said, this is not recommended at all. Better use \text:

\documentclass{article}
\usepackage{amsmath}
\usepackage{eulervm}
\begin{document}
\begin{align*}
\text{text} =
x_\sigma
\end{align*}
\end{document}


Instead of \text you can use \textrm or \mathrm (it depends on what you're really wanting to do).

Don't use align* as a substitute of equation* (or $...$), but this is another matter.

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Thanks for the reminder regarding align*. In the original code it was needed, and I wasn't sure whether or not it is part of the problem. –  Dror Jul 11 '12 at 9:16