Literal greek converts to wide-spaced MJX-TeXAtom-ORD

[flying-sheep]

Hi, the HTML renderer renders <span class=mrow><span class=mo>σ</span></span> with little space around it, but the MathML renderer creates <mrow class=MJX-TeXAtom-ORD><mo>σ</mo></mrow> which is far wider than the contained <mo/>.

i think it should rather render as <mi> like \sigma.

[dpvc]

Even the actual TeX program does not deal well with unicode characters outside the ASCII range (U-0000 to U-007F), and to get support for that, you need to use an extended version of TeX like XeTeX or LuaTex. MathJax's treatment of non-ASCII characters is only slightly better.

When MathJax sees a character that is not a special character (like \ or {), MathJax uses a pattern to tell if it is a letter (which are put in <mi>) and another one to tell if it is a number (which it puts in <mn>); everything else gets put into <mo>. The letter and number patters only create ASCII characters. But you can modify those patterns to include other characters, like the Greek letters. Add

<script type="text/x-mathjax-config">
MathJax.Hub.Config({
  TeX: {Augment: {Definitions: {letter: /[a-z\u0391-\u03A9\u03B1-\u03C9]/i}}}
});
</script>

to your page just before the script that loads MathJax.js itself. That will make upper- and lower-case Greek letters be treated as letters (rather than "other") and they will be put into <mi> elements instead.

[flying-sheep]

Many thanks for the workaround!

However, MathJax is used in too many places to not fix such things at the source.

Maybe MathJax wants to use XRegex or similar to get sane regexes that know that “ä”, “è”, and “α” are letters.

[dpvc]

This was fixed in v3 (v3.2 if I recall correctly).