Luatex and unicode math without unicode-math

Question

I'm using fontspec in lualatex to get a OTF main font, but I'd like to use one of the good old math fonts (like the default TeX one). After trying different packages, I didn't manage to make it work with utf-8 input:

\documentclass{minimal}
\usepackage{fontspec}
\setmainfont{TeX Gyre Pagella}
\begin{document}
Test for $\alpha$ and $α$.
\end{document}

This renders only the first math symbol correctly. What do I miss exactly?

Answer 1

You must declare the alpha. E.g. in fontmath.ltx the command \alpha is set up this way:

\DeclareMathSymbol{\alpha}{\mathord}{letters}{"0B}

You need the same declaration for the alpha (the ^^^^03b1 are only ascii substitutes for the alpha, you can replace them):

\documentclass{minimal}
\usepackage{fontspec}
\setmainfont{TeX Gyre Pagella}
\DeclareMathSymbol{^^^^03b1}{\mathord}{letters}{"0B}
\begin{document}
Test for $\alpha$ and $^^^^03b1$.
\end{document}

Answer 2

use the Latin Modern Math font:

\documentclass{minimal}
\usepackage{unicode-math,fontspec}
\setmainfont{TeX Gyre Pagella}
\setmathfont{lmmath-regular.otf}
\begin{document}
Test for $\alpha$ and $α$.
\end{document}