Index Coefficient + Wedge

[Nicolas Cresto]

Hello,

I would like to extract coefficients from expressions where the tensors are made of sub-objects, in my case some forms combined with the wedge product.

Since IndexCoefficient does not recognize these composite objects, the only way I can think of to circumvent this issue is to define a bunch of intermediate tensors and replace my forms by them. As you can imagine, when you have a lot of them, with different symmetry properties, it becomes messy.

Is there a way to make IndexCoefficient handle this kind of expressions?

Herewith a little notebook that shows the problem.

Thanking you in advance,

Cheers,

Nicolas

[Jose]

Hi,

Many thanks for reporting this. Indeed, IndexCoefficient (and more importantly the internal functions for SymmetryEquivalents) didn't know about products and their commutativity properties ("Commutative", "Anticommutative", "SuperCommutative", "SuperAnticommutative", ...). The "SuperXXX" cases mean that commutativity depends on the grades of the objects being commuted. For example, after loading xTerior we have

In[2]:= CommutativityOfProduct[Wedge]

Out[2]= "SuperCommutative"

I've added support for products in those missing places, but haven't tested it yet, other than very basic inputs. I've uploaded new tentative tarballs for the next version of xAct here:

https://www.xact.es/download/xAct_1.1.5.tgz or .zip

I'd appreciate if you can test this and let me know of any problems you may find.

Cheers,

Jose.

[Jose]

Sorry, I wrote an incorrect link. It should be:

http://www.xact.es/download/xAct_1.1.5.tgz or .zip

Jose.

[Nicolas Cresto]

Thank you very much Jose!

I'm a Mathematica beginner, so I'm far from exploiting all the power of xAct, but I'll see how it behaves in my algo and keep you up to date of any trouble I may stumble onto.

Thanks again,

Nico