How to use text within math as a macro without it being subject to \emph

Question

I'm working on a book and want to have certain special maps labeled "a" and "d" but not in the usual math font. The standard AMS fonts don't support too many special versions of lower-case letters, and I'm not a fan of the ones that do exist. I'm also trying to avoid installing a more exotic font package. After playing around for awhile, I decided that I liked using the boldface version of the ordinary text fonts in these situations, and since I will be using these often, I set up some elementary macro commands:

\renewcommand{\d}{\text{\textbf{d}}}

\renewcommand{\a}{\text{\textbf{a}}}

This mostly works out okay, except I noticed that within theorem statement environments my a and d are subject to the italicization of the current environment, so I don't get consistent characters. Is there a way to improve my macros to avoid this phenomenon?

Thanks!

Answer 1

The correct way is to use \mathbf and not \text{\textbf{...}}.

So

\newcommand{\ba}{\mathbf{a}}
\newcommand{\bd}{\mathbf{d}}

With \mathbf you select a math alphabet, which is not influenced by the current text font.

Don't redefine \a and \d; you've been warned. ;-)