[Tex/LaTex] Force upright Greek letters with isomath

greekisomathmath-moderoman

The isomath package makes it possible to typeset upright Greek letters via \mathrm and \mathbf. Is it it possible to force all Greek letters to be typeset upright unless specified otherwise, e.g. to make it so that \(\Phi \Psi\) delivers the same output as \(\mathrm{\Phi \Psi}\)? An ideal solution would be to load isomath with some option and if it optionally could make difference of upper and lower case Greek letters.

\documentclass{article}

\usepackage{isomath}

\begin{document}

\(\Phi \Psi\)% These are typeset in italic

\(\mathrm{\Phi \Psi}\)% These are typeset upright

\end{document}

Output of code producing Greek letters

Best Answer

You don't need the isomath package:

\DeclareMathSymbol{\Gamma}{\mathalpha}{operators}{0}
\DeclareMathSymbol{\Delta}{\mathalpha}{operators}{1}
\DeclareMathSymbol{\Theta}{\mathalpha}{operators}{2}
\DeclareMathSymbol{\Lambda}{\mathalpha}{operators}{3}
\DeclareMathSymbol{\Xi}{\mathalpha}{operators}{4}
\DeclareMathSymbol{\Pi}{\mathalpha}{operators}{5}
\DeclareMathSymbol{\Sigma}{\mathalpha}{operators}{6}
\DeclareMathSymbol{\Upsilon}{\mathalpha}{operators}{7}
\DeclareMathSymbol{\Phi}{\mathalpha}{operators}{8}
\DeclareMathSymbol{\Psi}{\mathalpha}{operators}{9}
\DeclareMathSymbol{\Omega}{\mathalpha}{operators}{10}

To get an italic Gamma, use \mathnormal{\Gamma}. Try

$\Gamma\mathnormal{\Gamma}\mathbf{\Gamma}$

enter image description here

The command \DeclareMathSymbol is used for assigning a meaning to characters or commands in math mode. The second argument contains the "kind" of symbol; \mathalpha means a symbol that obeys to the alphabet selection commands. The third argument is the alphabet used by default; the fourth is the slot in the font. All the standard declarations are in fontmath.ltx loaded at format creation time.

Notice that these declarations won't work if the default font encoding of the document is T1 instead of OT1, as operators refers to the ordinary Roman document font. One should define a new math alphabet, in this case.

How to do this when the document encoding is T1? One has to define a new symbol font:

\DeclareSymbolFont{otone}{OT1}{cmr}{m}{n}
\SetSymbolFont{bold}{otone}{OT1}{cmr}{m}{n}
\DeclareMathSymbol{\Gamma}{\mathalpha}{otone}{0}
\DeclareMathSymbol{\Delta}{\mathalpha}{otone}{1}
\DeclareMathSymbol{\Theta}{\mathalpha}{otone}{2}
\DeclareMathSymbol{\Lambda}{\mathalpha}{otone}{3}
\DeclareMathSymbol{\Xi}{\mathalpha}{otone}{4}
\DeclareMathSymbol{\Pi}{\mathalpha}{otone}{5}
\DeclareMathSymbol{\Sigma}{\mathalpha}{otone}{6}
\DeclareMathSymbol{\Upsilon}{\mathalpha}{otone}{7}
\DeclareMathSymbol{\Phi}{\mathalpha}{otone}{8}
\DeclareMathSymbol{\Psi}{\mathalpha}{otone}{9}
\DeclareMathSymbol{\Omega}{\mathalpha}{otone}{10}

Of course cmr can be changed into the document's main font family name, provided it contains Greek uppercase letters in its OT1 version; but it's just a matter of giving the correct slot numbers for the chosen font.

Related Solutions

[Tex/LaTex] Upright Greek letters in text mode (not upgreek)

You can pass the options [greek,english] to the babel package. Then you can switch between them using \greektext and \latintext.

\documentclass{minimal}
\usepackage[greek,english]{babel}
\begin{document}

\greektext
A whole paragraph in greek letters
\latintext

% If we only want a single letter, it might make sense to define commands:

\newcommand{\ga}{\greektext a\latintext}
\newcommand{\gA}{\greektext A\latintext}

\gA lph\ga
\end{document}

greek and english letters

[Tex/LaTex] How to get upright greek letters with the mathastext package

As pointed out by @DavidPurton in a comment, the documentation of mathastext indicates (but in a not so clear way) that upgreek option has effect only if one of the Greek related options described in §1.9 Greek letters is active.

For example:

\documentclass{article}
\usepackage[upgreek, LGRgreek]{mathastext}
\usepackage{bm}

\begin{document}
\[\phi, \Phi\]
\[\bm{\phi}, \bm{\Phi}\]
\end{document}

Output:

However, perhaps your font set-up has some specifics.

Other approaches

E.g. you could use \usepackage[upright]{fourier}...load text packages...\usepackage{mathastext} to benefit from the Fourier set-up for Greek letters. Then \bm{\phi} gives a bold upright Greek letter. mathastext does not interfere at all in this.

\documentclass{article}
\usepackage[upright]{fourier}
% add here text packages according to what is needed
\usepackage{mathastext}% does not modify anything to Greek in math
\usepackage{bm}

\begin{document}
\[\phi, \Phi\]
\[\bm{\phi}, \bm{\Phi}\]
\end{document}

Produces:

Or use eulergreek option:

\documentclass{article}
\usepackage[eulergreek]{mathastext}
\usepackage{bm}

\begin{document}
\[\phi, \Phi\]
\[\bm{\phi}, \bm{\Phi}\]
\end{document}