# newtxmath package disrupting blackboard bold greek characters

I'd like to use some sort of blackboard bold capital Delta in a large TeX file. In the past I've used to code displayed below to typeset it, but when I include a new package "newtxmath,newtxtext" that I'm using for some special characters, it changes the display from the usual blackboard bold Delta to a normal boldface Delta. Blackboard bold numerals 1, 2, ... are unaffected.

\documentclass{amsbook}
\usepackage{newtxtext,newtxmath}%\normalfont\Nearrow
\usepackage{amsfonts, amsmath, amssymb}

%special blackboard bold characters
\newcommand{\bbefamily}{\fontencoding{U}\fontfamily{bbold}\selectfont}
\newcommand{\textbbe}[1]{{\bbefamily #1}}
\DeclareMathAlphabet{\mathbbe}{U}{bbold}{m}{n}

\def\DDelta{{\mathbbe{\Delta}}}
\newcommand{\1}{\mathbbe{1}}
\newcommand{\2}{\mathbbe{2}}

\begin{document}

$\1$ and $\2$ and $\DDelta$ and $\mathbbe{\omega}$

\end{document}


Can anyone help me figure out what is going on?

Bonus question: I'd love to also be able to typeset a blackboard bold lower-case omega.

• I get the same output (apart from the text font, of course) with or without newtx{text|math}. You never get a blackboard bold omega; for that something more would be needed. – egreg Jan 15 '16 at 13:00
• That's strange. For me, when those packages are commented out, I see a capital blackboard bold Delta, with the left-diagonal edge duplicated. When those packages are included, I see a boldface Delta, with the right-diagonal edge thicker than the other two. – Emily Riehl Jan 15 '16 at 17:42
• Update: By checking error logs produced when I compile, I think the issue with the blackboard bold Delta has to do with some font resizing or something with the newtxmath package. When I remove that package but keep the newtxtext one, the font resizing doesn't happen for some reason, so the blackboard bold Delta looks like it should. I guess that, plus the \usepackage[bbgreekl]{mathbbol} suggested below, solves the problem. – Emily Riehl Jan 25 '16 at 14:18

Use \usepackage[bbgreekl]{mathbbol} in the preamble. Hollow omega (or any other minuscule Greek letter) can be typed with \bbomega. [For hollow epsilon, use \bbespilon.]

• Thank you. I'm very happy with the \bbomega and appreciate the warning about "espilon". – Emily Riehl Jan 25 '16 at 14:15

Not a solution, but more of an explanation:

There are two issues:

1. by default \omega is defined not to react to math alphabet (contrarily to \Delta). This is the default situation without any package and is not changed by your loaded packages.

2. in font bbold in U encoding (see file returned by kpsewhich Ubbold.fd for the specific tfm filenames), there is no omega at the default location occupied by \omega (slot 33), rather it contains there a blackboard bold exclamation point.

Check with:

\documentclass{amsbook}
\usepackage{newtxtext,newtxmath}%\normalfont\Nearrow
\usepackage{amsfonts, amsmath, amssymb}

%special blackboard bold characters
\newcommand{\bbefamily}{\fontencoding{U}\fontfamily{bbold}\selectfont}
\newcommand{\textbbe}[1]{{\bbefamily #1}}
\DeclareMathAlphabet{\mathbbe}{U}{bbold}{m}{n}

\def\DDelta{{\mathbbe{\Delta}}}
\newcommand{\1}{\mathbbe{1}}
\newcommand{\2}{\mathbbe{2}}

% check in the (long) compilation log lines containing XXXXXXX to find
% some info on this modification to let \omega obey math alphabet:
\typeout{XXXXXXX Current meaning of \string\omega: \meaning\omega}
\count255\omega
\mathchardef\omega\numexpr \count255+"7000\relax
\typeout{XXXXXXX New meaning of \string\omega: \meaning\omega}

\begin{document}

$\1$ and $\2$ and $\DDelta$ and $\mathbbe{\omega}$

% for testing
% \ttfamily
% \meaning\omega

% \meaning\Delta
\end{document}


which produces:

Playing with pdflatex nfssfont (but see (*) next) one finds the blackboard omega in slot "7F (127). You can obtain it in your set-up with \mathbbe{\mathchar"717F} but it would be more appropriate to define a Symbol Font rather than a math alphabet.

(*) Last thing: it is not clear what you mean by "bold" as your math alphabet uses m not b or bx for the series. Isn't there a package to use font bbold? Ah yes, texdoc bbold tells me there is package bbold and the contents of bbold.sty is actually copied with a renaming in your code. There is no boldened variant it seems.

You could use package bm to bolden the symbols, but there are surely better alternatives. Anyhow, "blackboard bold" was obviously not used to mean "bold blackboard bold" ...

• Package mathbbol mentioned @SammyBasu's answer provides indeed the needed interface. It does \DeclareSymbolFont{bbold}{U}{bbold}{m}{n} and \DeclareMathSymbol{\bbomega}{\mathord}{bbold}{"7F} among other things. Had I read that I could have spared contributing this slightly off-the-mark answer... – user4686 Jan 26 '16 at 7:19