4

Apologies for such a specific question. I am using the newtx fonts. For some reason, it seems that newtxmath ignores the trema (ddot) in math mode when using \operatorname or even just \mathrm. Here is a sample document:

\documentclass[a4paper,10pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{newtxtext,newtxmath}

\begin{document}
$\mathrm{\ddot{o}}$
$\operatorname{M\ddot{o}bius}$
\end{document}

This produces:

o Mobius

instead of the desired

ö Möbius

As an alternative, I could instead use \textup{M\"{o}b} which works. But I'm sure there is a reason \operatorname is preferable to \textup, although I'm not expert enough to understand it.

  • By the way, \ddot{\mathrm{o}} inserts double dots over o. – Sigur Jan 20 at 21:59
  • In the case of "Möbius", ,that's strictly speaking an umlaut, not a trema, since it doesn't serve to change what would otherwise be a diphthong. – phipsgabler Jan 21 at 7:43
  • @phipsgabler I was told by my German teacher that trema refers to the sign, while umlaut refers to the sound change. Maybe she was wrong. – Seub Jan 21 at 9:23
  • Hm, a valid point from a typographic perspective. On the other hand, we practically never refer to the dots themselves, since the whole letter is considered a separate grapheme, distinct from <o>, and not as an <o> with diacritics. And it is either pronounced as "Umlaut-O", "Umlaut-Ö", or simply [øː], never as "O with dots", as in other languages. (The usage of "trema" exclusively for diphthong separation might just be a personal bias from my knowledge about classical Greek, though...) – phipsgabler Jan 21 at 9:55
4

This works:

\documentclass[a4paper,10pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{newtxtext,newtxmath}

\DeclareMathOperator{\mobius}{M\mathnormal{\ddot{\mathrm{o}}}bius}

\begin{document}

$\mobius$

\end{document}

enter image description here

5

With the default setup you need to use the text accents not math so \textrm{Möbius} but \operatorname gives "log-like" prefix operator spacing, so to get the effect of that, wrap in the primitive \mathop command, so

\mathop{\textrm{Möbius}}

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