[Maxima] question about ctensor

Viktor T. Toth vttoth at vttoth.com
Sun Dec 2 09:28:53 CST 2007


I don't think there is a bug, but please feel free to check and let me know
if you think otherwise!

The index ordering (for the Riemann tensor, in particular) that is used by
ctensor is somewhat peculiar. We inherited it from the "old days", and I did
not think it's a good idea to change it. Perhaps I should have, but I was
trying to fix what was broken, not reinvent the wheel.

Some details of the tensor packages (including the actual definition of
specific tensors like the Riemann tensor, using the same index ordering
that's used in ctensor/itensor) can be found in a paper I put on arXiv some
two years ago, cs.SC/0503073. Consider it a supplement to the
atensor/ctensor/itensor manual pages.


Viktor


-----Original Message-----
From: maxima-bounces at math.utexas.edu [mailto:maxima-bounces at math.utexas.edu]
On Behalf Of Evan
Sent: Sunday, December 02, 2007 9:35 AM
To: maxima at math.utexas.edu
Subject: [Maxima] question about ctensor

I tried ctensor with the Robertson-Walker metric.

Following the definition of Riemann curvature tensor in the document
of ctensor, it seems that the Ricci tensor given by maxima is negative
what it should be.

The document doesn't give explicitly the definition of the Ricci
tensor, and I only ever see one definition as in
http://mathworld.wolfram.com/RicciCurvatureTensor.html

Is there a bug or I missed something?
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