[texhax] derivatives and integrals: math operators

[Xavier Gracia Sabate]

On 08/06/2009 at 03:58 PM, Natercia Fernandes <natercia at eq.uc.pt> wrote:

> Math operators should be typeset in upright letters and also have a special
> spacing.
> So shouldn't the "d" of derivatives (or integrals) be set with upright
> letters, since both are mathematical operators?

In differential geometry "d" is frequently used for the
exterior differential operator. As such, some people
(including myself) typeset it in upright letters.
This "d" is not sinply AN operator, but a specific
(and very important) one.  I use the same convention
for other one-letter operators (as the tangent map, or
the jet bundles).
The "d" in integrals has a meaning close to that of
differential geometry, and therefore I also put it
upright.

(By the way, the judgement on a notation should be
based on its usefulness and coherence, and not on who
is presumed to use it.  I also support putting the
differential next to the integral sign, for reasons 
that have already been exposed.)

Xavier Gracia
Faculty of Mathematics and Statistics
Technical University of Catalonia