Blackboard type \Omega symbol

Question

I would like to produce a capital Greek letter \Omega in blackboard type font. This is related to the question: Is there a blackboard version of Omega (the capital letter). However, this one has been marked as answered whereas I do not find it really true. In particular, the related answer proposes e.g. using \bbm which does not work for me.

An alternative would be to use \bbold. My problem is that I want to use \mathbb for my text and only \bbold to define my capital letter. So I try this at the beginning of my document:

\usepackage{bbold}
\newcommand{\OO}{\bb{\Omega}}

But I have two problems: first, \bb{\Omega} does not seem to be the solution to produce my capital letter; on the other hand, I do not know how to use again \mathbb after having defined my \OO symbol.

Any suggestion would be appreciated!

Answer 1

A simple solution is to declare another “math alphabet” with a different name:

% My standard header for TeX.SX answers:
\documentclass[a4paper]{article} % To avoid confusion, let us explicitly 
                                 % declare the paper format.

\usepackage[T1]{fontenc}         % Not always necessary, but recommended.
% End of standard header.  What follows pertains to the problem at hand.

\usepackage{amsfonts}

\DeclareMathAlphabet{\mathmybb}{U}{bbold}{m}{n}

\newcommand*{\R}{\mathbb{R}}
\newcommand*{\BOmega}{\mathmybb{\Omega}}



\begin{document}

The usual~$\R$.
The boldfaced omega: $\BOmega$

\end{document}