xAct Tensor Computer Algebra

Dear all, I am using xPand to compute the tensor perturbations in a theory with higher derivatives.

Hi! This depends a bit on how complicated expression you should be able to handle, but to handle some

Hello, everyone I write this post because I have a problem when computing variations with 'xPert

Hi, There are several ways to do this. A possibility is to use xTensor's internal tool to define

Hi! In general it is not a great idea to make rules that tries to replace several terms with

thank you for your alternative proposal! Thomas Bäckdahl schrieb am Donnerstag, 9. März 2023 um 17:13

Hi! This seems a bit annoying. Unfortunately Solve can do some random choices. To be sure that you

oh..this is great..thanks everyone.. this helps a lot On Wednesday, March 1, 2023 at 6:56:18 AM UTC+5

Hi Jose, Thank you for your feedback. Sorry for the late reply. I was traveling. Fortunately, I

Hello, How can we perform the holographic renormalisation of U(1) gauge field in the asymptotically

Hi, This behavior is expected in all of xAct. Every symbol used must be defined with a unique type,

Hi Nitol, I'm not sure how you wanted to use VarD to integrate by parts and discard total

Hi, Yes, you can define tensor fields with indices in different vector spaces, like two tangent

Hi, There were three issues: 1) You were using a phi function without first declaring it with

Hi, Answers inlined. On Wednesday, February 8, 2023 at 6:56:06 AM UTC-6 salvam...@hotmail.com wrote:

Dear José, Thank you very much for your quick and informative reply. I agree that (error-free) tensor

Hi, You are starting with the perturbation of Riemann[a, b, c, d], instead of the natural Riemann[-a,

Hi, This computation is too large for me to absorb and debug, but let me say this: You are calling

Hi again, This post is essentially equivalent to https://groups.google.com/g/xAct/c/zDHXAdP9Bp4?hl=en

Hi, xCoba has two main modes of work: what I call the TensorValues framework and the CTensor

Hi, xTensor (and by extension of all xAct) works primarily with the Times product, which is

Hi! Yes! For me too. I hope people find these posts useful to customize objects in xAct. Many thanks!

Thank you so much, it was really helpful! I guess I will have to deal with my little monster tensor

Hi, Good day. I need a help in knowing what exactly the metric form that used in xPand packages, is

Dear Dong-han, I'm not very familiar with xCoba, so I'm not sure if what I'm writing

Thank you. That makes sense. On Tuesday, December 20, 2022 at 9:06:13 AM UTC-6 Jose wrote: Hi, See

Hi, In that case I recommend to use the xPand package which goes on top of xTensor/xPert. It allows

Hi Jose, ok I see, thank you very much. You use Perturbed[ ] which gives you the full expansion. I

Hi, Thanks. The notebook can be downloaded here: http://xact.es/xAct_RDLiveStream.nb Cheers, Jose. On

Hi Salva, No, there is no explicit support for complex charts in xCoba. I think you would have to