Basically I want to use the symbol of \lambda in \documentclass{acmart} in a different document class without changing any other symbols.
(I'm the guy from a previous question who asked about using \lambda from the txfonts package, apparently it was a very similar lambda but not the one I was looking for, thanks)
The idea is the same as in the previous answers, but there are further complications, I'm afraid, because acmart uses newtxmath with the libertine option. The first step suggested in the other answer gives the same result, whereas the second one shows
> \OML/nxlmi/m/it/9 .
But here it's not sufficient to replace txmi with nxlmi, because the font definition file takes different paths according to the options newtxmath is loaded with.
In this case it's simpler to add the font definitions manually.
\documentclass{article}
\usepackage{amsmath}
\DeclareFontFamily{OML}{nxlmi}{\skewchar\font =127 }
\DeclareFontShape{OML}{nxlmi}{m}{it}{
<-6.3> nxlmi035
<6.3-8.6> nxlmi037
<8.6-> nxlmi03
}{}
\DeclareRobustCommand{\varlambda}{\text{\usefont{OML}{nxlmi}{m}{it}\symbol{"15}}}
\begin{document}
$\alpha\beta\lambda\varlambda$
\end{document}
This is what you get with \documentclass{acmart} and just $\lambda$ in the document body.
