5

A minimal working example is as follows:

\documentclass{amsart}
\begin{document}
\Huge

$$\phi$$

\end{document}

Question: How to invoke \phi only from newtxmath package? Note that I don't like to invoke any other letters from newtxmath. Any help is welcome!

9

There you go.

\documentclass{amsart}
\DeclareSymbolFont{ntxletters}{OML}{ntxmi}{m}{it}
\SetSymbolFont{ntxletters}{bold}{OML}{ntxmi}{b}{it}
\DeclareMathSymbol{\phi}{\mathord}{ntxletters}{30}
\usepackage{bm}
\begin{document}
\Huge

\[\phi, \bm{\phi}\]

\end{document}

phi


Thanks to @marmot pointing out this previous answer by @AlanMunn. As @AlanMunn said in that answer, one needs some basic knowledge about font declarations before performing the trick. This key line of code in newtxmath.sty:

%\DeclareMathSymbol{\phi}{\mathord}{letters}{30}

tells us that we should be looking for lines that declare letters. Indeed, we find

%%%%%%%%%%%%%%%
% Math Italic %
%%%%%%%%%%%%%%%
... ... ...
    \DeclareSymbolFont{letters}{OML}{ntxmi}{m}{it}
    \SetSymbolFont{letters}{bold}{OML}{ntxmi}{b}{it}
... ... ...

Thus, the suggested solution.

2
  • 1
    It's important to find ntxmi! Although I know the method, but I didn't find ntxmi!
    – M. Logic
    Oct 2 '18 at 11:37
  • Very kind Ruixi...marmot not exist..but there's his substitute :-) Maybe you should edit the answer since there are no comments referring to the two users.
    – Sebastiano
    Dec 28 '19 at 22:42

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