[rotation] Request for Comment -- Nomenclature Guidelines

Alain Cochard alain at geophysik.uni-muenchen.de
Fri Jan 25 06:58:23 CET 2008


Hello group, hello Charles.

Charles Adam Langston (clangstn) writes:

  > Thus, there are no "pseudovectors" and the signs are perfectly defined
  > by the curl.

I don't understand this statement.  Maybe it's a matter of
terminology, but to me the curl, like any cross product of true
vectors actually, is indeed a pseudovector.  Of course I agree when
you say that "Once the Cartesian coordinates have been defined,
rotation is exactly defined", but the fact remains that the
transformation rules for these kind of vectors (also called axial
vectors) are not the same as those for true or usual vectors.
Sometimes the distinction needs to be made.  For example, if one
changes the sign of the basis vectors, trues vectors u and v are
changed into -u and -v, but the cross product is invariant.

I've heard people arguing they shouldn't be called pseudovectors in
the first place, since the 'pseudo' quickly disappears.  They are not
rank-1 tensors, but antisymmetric rank-2 tensors.

Or maybe I'm totally confused...

Regards,
Alain




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