XITS and \not\models

Question

When using XITS (with xelatex), the \not is displayed way too high on certain commands. For instance:

\documentclass{standalone}
\usepackage{unicode-math}
\setmathfont{XITS Math}

\def\nerode{\equiv}
\begin{document}
\huge$\not\models \not\nerode \not\equiv$
\end{document}

is displayed:

That is, only the \not\equiv which is probably a glyph by itself, is properly printed. Compare the above result with the following (without unicode-math and XITS Math):

What is the way to go to fix that?

Thanks!

Answer 1

unicode-math should load predefined negation symbols when available, so \not\equiv is the same as \nequiv, but it seems not all aliases were taken care of (\not\vDash works but not \not\models).

unicode-math simply defines \not so that it checks the next csname, and if the there an n or not prefixed csname of that name, it will use it, else it will just put the slash.

A simple fix is to define \n… csnames of the ones that does not work for you, e.g.:

\let\nnerode\nequiv
\let\nmodels\nvDash

Answer 2

Usually \not is only a poor man's solution, overlaying a slash like glyph with the relational symbols that follows. However, the result could be improved by ligatures to select the right glyph. Probably this is the case with \not\equiv here.

Both negated characters are directly available. And in unicode-math-table.tex the macro names can be found:

• ≢: U+2262 NOT IDENTICAL TO: \nequiv
• ⊭: U+22AD NOT TRUE: \nvDash

Thus they can be used directly:

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{XITS Math}

\begin{document}

$\nvDash\nequiv$ % standard names (unicode-math-table.tex)

$⊭≢$ % direct

\end{document}