xAct Tensor Computer Algebra

Hi everyone, I'm trying to derive a specific expression involving derivatives with respect to the

Hi I am not sure I understand what you want. Is your dX factor fixed? You have defined it as a 1-form

Thank you Juan, it works fine. суббота, 30 августа 2025 г. в 22:53:44 UTC-3, Juan Margalef: As a

One can, if one wishes, remove the "quarantine" attribute from the current version of xPerm

Hi Thomas Bäckdahl, I really appreciate your reply. I used the following: DefConstantSymbol[dim,

Hi I added into your file here "approach 3" which contains my answer. The modified file is

Hi All, Now that Wolfram Language 14.3 has been released, I'd like to upload a new version of

Hi! All of these things are manifestations of evaluation control in Mathematica. If you write

I am glad!! Just for future reference, what I did was to take the file xPert.nb, look for

Hello guys, I'm trying to derive the modified Tolman-Oppenheimer-Volkoff (TOV) equations for a

In my xAct project using Mathematica, I encountered an issue while constructing a 4×4 matrix using

Hi Barry, Thank you for your reply. If possible, I'd like to sign up for a notification in case

Thank you for your help. Have a nice day Il ven 11 lug 2025, 13:13 Jose <jo...@xact.es> ha

Hi everyone, I am using Cyril Pitrou's ActionVariation_Metric_Fields.nb on xAct-contrib/examples

Hi Alejandro. It is hard to check your notebook since it is not selfcontained, try to add all the

Hi , Just to add that TInvar (like Invar before it) only knows about the Bianchi identity for the

Changing the definition might be too complicated and have unexpected consequences. I would recommend

Hello! I realise that this is an old question but I recently tried to tackle the same problem so I

Hi! If the name of your tensor is JJ, you can try things like Collect[ScreenDollarIndices[%], {JJ[__]

Hi! First of all it is PairQ, not Pair. Secondly, as I said, you should not use conditions in

Dear Teake, Thank you for your reply. You said "For the particular case in the Gauss-Bonnet

Hello, I am trying to compute the partial derivatives, in a given chart S, of the basis vectors from

Hello, Given a particular identity for expressions in terms of the Riemann/Ricci tensors and the

Dear colleagues, how are you? We are working with a symmetric rank-3 tensor field, h_{\mu\nu\rho},

Thanks Alfonso, indeed it did work. Regards, Max On Monday, May 19, 2025 at 10:48:43 AM UTC-4 Alfonso

Ah, I see. Thank you very much for catching the mistake. I do have a follow up question on this now.

Hi Juan, this works wonderfully. Thanks. Also, thanks for the plausible clarification as to why it

Hi everyone, I'm having trouble with obtaining the equations of motion for DCS theory. According

Hi Eran. I am afraid there are several mistakes. 1. The use of components requires the package xCoba.

Hi! You don't have to use just symmetric, or antisymmetric groups. You can specify any list of