[PRL] Tex Question: Bold font for Greek letters

[Richard C. Cobbe]

Lo, on Monday, April 26, Kenichi Asai did write:

> Hi,
> 
> Does anyone know how to write Greek letters in bold font or any other
> forts (in math mode)?  I tried $\mathbf{\lambda}$ but it seems it does
> not work.  I want to express lambda terms that use \lambda, @, \xi,
> \langle, and \rangle in two different fonts (to distinguish the object
> language from the meta language).

\boldmath $\alpha$

Three notes:

  1) \boldmath is a declaration; it lasts until the end of the nearest
     enclosing group.

  2) For reasons I don't fully understand (and almost certainly don't
     want to), you can't use \boldmath in math mode.  If you want a bold
     subformula, you have to use this hack:

            $\mbox{\boldmath$\lambda$}x.x$

     See pp 51--52 of the Lamport book, once we unpack it.

  3) At least with the computer modern fonts, the difference between
     normal \langle and boldfaced \langle is pretty subtle; the same
     holds for \rangle.  Try it out and see, but you may want to think
     about a different typographical convention in this case.

     (In other fonts, it's worse.  I just tried this with
     \usepackage{mathpazo}, and I couldn't detect any difference between
     them at all.)

Richard