xAct Tensor Computer Algebra

Thank you very much, Ilham, for your help. I will carefully analyze what you wrote to me. El jueves,

You can use SortCovDs in the definition when doing the perturbation before doing ToCanonical Collect[

Apologies for my mistake, in the previous email I attached the wrong file. I am now attaching the

Hi, Can anyone recommend me a way to extract components from a row matrix when using xCoba? My code

Hello, I have a list of terms in which a couple of them have the same index structure and they differ

Hi, Thanks for creating that mirror, Konstantinos. Something has changed again in the xact.es domain

Hey ! How to do it with a tensor field and not a scalar field ? Le lundi 22 juillet 2024 à 10:41:16

Hello, I need to compute the canonical momenta associated to the metric components. I want to

Dear Armando, After two days of confusion this indeed resolved the problem. Compared with your

Hello, When defining a rule using EqToRule, is it possible to add a condition for the rule to work?

Hello! I am new to xPert as well as xAct, and I have a simple question: DefManifold[M, 4, {a, b, c, d

Hi Thomas, Thank you very much for your reply! It has been very helpful. I have two questions.

Hello everyone, I am fairly new to Mathematica and xAct and were not able to find my answers in the

Hello everyone. This is my first post in this community. I am learning some features of xAct,

Hello, If one wants to apply the command AllContractions to a list of terms each of which contains an

Hi, Has anyone come up with a (hopefully simple) solution to this problem? (See thread) It is a bit

Thanks José, your fix indeed works. Max On Thursday, November 7, 2024 at 9:56:53 PM UTC+1 Jose wrote:

Hello everyone (I am new). I just started to learn xAct (with xPert, xTras, etc), and I am trying to

Hii, I am using xPPN package where for higher order perturbation it generates square terms with the

I have my vierbeins as: e^{0}_{i} = a(t)\partial_{i}\beta, e^{a}_{0} = \partial_{a}\zeta, e^{a}_{j} =

Hi together, I am programming a notebook with xact for calculations with tetrads. The tetrad is

Dear Leo, Thank you for your reply. I tried the command SortCovDsToBox /@ unsorted and it did not

Hi together, I am currently setting up an xAct notebook to work with tetrads, and stumbled over a

Hi everyone, I have a question about submanifold. I have a surface in R^3 with the curvilinear

Hey, I have been trying to work with xPPN package. Where I have got to face major problem. I hope you

Hi! Can you please provide a small non-working notebook that shows the problem? If you are mixing

Hi, I see, thanks! Now whenever I use FullSimplification[], I apply ScreenDollarIndices right after

Hi, Thanks a lot for giving those two ways to achieve the goal! They both work fine. I too wondered

Hi, Thank you very much! Cheers Sukruti On Monday 23 September, 2024 at 4:52:23 am UTC+2 Jose wrote:

Hi! Higher order NP derivatives should work without extra care. If you use //. NPDerivativeRules