Re: Implementation Question -- SL(2,C)

Patrick D. F. Ion wrote:
> The case of SL(2,C) brings up a couple of questions aside from accents.  I
> note that Robert's  display list shows a bold C, presumably for the complex
> numbers, as, for instance, MR style prescribes.  However, many choose a
> blackboard bold or doublestruck font, and so then there's an argument for
> hoping that people might consider a math entity ℂ which the
> reader could display in the locally favored way.

It makes the most sense for the conceptual entity "the complex numbers"
to be represented by a separate named entity.  It is certainly *not* a
variable named "C" in any sense -- and you would need it to be distinguished
for it to be properly rendered to speech.

> In contrast to MR, Robert did not choose to put the _abbreviation_, SL,
> naming the classical Special Linear group in roman, as opposed to a
> presumed italic within a mathematical expression.  Again one could argue
> here for a math entity &SL;.

Definitely.  Again, the "SL" represents an entity with a special meaning
taken from convention, not just something named "SL".  It should be
indicated that way.  Because there are so many entities with special
meanings in various scopes of discourse, this is another argument why
extensibility is needed very early.  The author of this article could
simply include a with the paper a small context definition that defined
the entity "SL", and gave simple rendering instructions.

I envision a setting where, if you are reading this paper and notice
that SL is an entity (say, because it is highlighted in some distinctive
colour), but don't know what it means, you can ask "what does SL
stand for?"  In a windowed GUI, you might do this by moving your
mouse over the SL; then a small popup would explain "Special Linear
group", with the text taken directly from the context definition.

This is the purpose of a context definition.