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MathGroup Archive 2002

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comments and questions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg35280] comments and questions
  • From: "Stanislaw Ewert-Krzemieniewski" <ewert at arcadia.tuniv.szczecin.pl>
  • Date: Sat, 6 Jul 2002 05:44:24 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Sirs,
I have the following permanent problems with MathTensor:

1) Running Mathematica 4.1  AddIndexTypes does not work.

2) Running Mathematica 2.2.3  DefineTensor[ T, {{1,2}, 1}]  yields
something like

PermWeight :: def: Object T defined
Get::noopen: Can't open /t549559

and T[li,lj]  does not look like a tensor component.
Messages of such type (i.e. Can't open ........ ) appear after some
other commands.

There are no such problems when running Mathematica 2.2.1. DOS version.

I have also found three things which look like errors:

1) When Rcsign  = -1 (like Eisenhart) the Weyl conformal curvature
tensor is not defined properly.

MapAll[ Simplify , Metricg[uh,uk] ( WeylC[lh,li,lj,lk] /.
WeylToRiemannRule) //CanAll // Tsimplify]

does not give 0.

2) SameQ[ RiemannR[la,lb,la,ld], RiemannR[la,ld,la,lb] ] gives False.
    One more condition should be added in definition.

3) Metricg[uh,uk] TraceFree RicciR[lh,lk] // CanAll // Tsimplify  does
not vanish.

Yours faithfully
Stanislaw Ewert-Krzemieniewski




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