xAct Tensor Computer Algebra

The problem is that Perturbation[B[_],0] returns B[_] and when you make the rule to put that to zero,

*T instead of F, sorry. On Tuesday, March 18, 2025 at 12:01:57 PM UTC+1 Nicola Arepo wrote: Hi

Hello all! In the following code: << xAct`xTensor` DefManifold[M, 4, {a, b, c, d, e, f, h, i, j

Greetings Barry, It's good to see new and expanded functionality being added to the xAct suite! I

I think I have found a bug in SeparateMetric: << xAct`xTensor` DefManifold[M, 4, {a, b, c, d}]

Hey, I'm dealing with a problem where after some tensor computations, I get the output: 1/4 q[-a,

Hello, Any suggestions for how to define the two Bianchi identities shown in the attachment, in order

Hi Sukruti, Currently TInvar only supports dual invariants (involving the epsilon tensor) for scalars

I think I managed to do the needed computation, and I attach it in case it might be useful for

Thank you! I totally missed those CDT's, and I wasn't familiar with IndexSet. Is there any

Hi Jose, Thank you so much for that short and elegant optimization! The code works very well now.

Hi, ToCanonical reorders free indices only as dictated by symmetry. Something like RiemannCD[-a, -d,

Hello xAct community, I'm trying to expand the Schutz-Sorkin action up to seconde order in scalar

Hello, When we have terms consisting of the Riemann/Ricci tensors and the Ricci scalar only, we can

Dear Debojyoti, As mentioned in a previous email to Gustavo, for a 4D spacetime, the Gauss-Bonnet (GB

Yeah! It makes total sense. Thanks for the quick reply :D El lunes, 17 de febrero de 2025 a las 12:07

Dear all, Good day, I am trying to use xcoba to compute the Levi-Civita connection of 1st the 2nd

Dear Leo, This solves the problem. Thank you so much! Best, Klaud On Wednesday, February 12, 2025 at

Thanks Markus, that worked! On Monday, February 10, 2025 at 11:53:55 AM UTC Markus B. Fröb wrote:

Hi all, I have a question about coordinate transformation using xCoba. My ultimate goal is to solve

Dear Colleagues, I am currently working with a four-dimensional representation of a specific Lie

Hello, I would like to prove the transformation law for the Christoffel symbol using the xAct tool:

I think I found a solution to display a specific component: https://mathematica.stackexchange.com/a/

Hi, One of the options of DefTensor is Dagger, with default Dagger -> Real, which is why tensors

Hi, A replacement such as PD[m] -> PD[m] + ie A[m] is problematic for because it needs patterns,

Hi, By default ToCanonical has option UseMetricOnVBundle -> All, which allows it to move indices

Thank you very much. I will review in detail what you wrote El lunes, 3 de febrero de 2025 a la(s) 3:

Hi, There are two potential problems you may want to address in your definition. 1) To avoid repeated

Hi, There is no support for such a definition in terms of the inverse metric. If you are going to

With due respect, I would like to kindly request your guidance on how to correctly define the f(G)