Re: [xAct] Wedge Product of a p-form with Itself

[Leo Stein]

Hello,

An odd form wedged with itself always vanishes; but while an even form *may* vanish when wedged with itself, this is not always true. Simple example below (where I have converted the Mma output to human-readable form):

In[]:= Needs["xAct`xTerior`"] 

In[]:= DefManifold[M4, 4, IndexRange[a, q]] 

In[]:= DefChart[Ch, M4, {0, 1, 2, 3}, {T[], X[], Y[], Z[]}]

In[]:= {dT, dX, dY, dZ} = Diff /@ ScalarsOfChart[Ch]

In[]:= w1 = Wedge[dT, dX]

In[]:= w2 = Wedge[dT, dX] + Wedge[dY, dZ]

In[]:= ToCanonical@Wedge[w1, w1]

Out[]= 0

In[]:= ToCanonical@Wedge[w2, w2]

Out[]= 2 dT ^ dX ^ dY ^ dZ

On Wed, Sep 13, 2023 at 9:07 AM Ashiqul Islam Dip <a.isl...@gmail.com> wrote:

Dear xTerior developers,
I was just getting started with xTerior package and tried wedge product. xTerior returns zero for a wedge product of an odd p-form with itself, but not for an even p-form. Shouldn't it return zero for a wedge product of any p-form with itself? Am I missing something?
Thanks in advance.

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