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xAct Tensor Computer Algebra
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xAct Tensor Computer Algebra
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wagno cesar
Mar 21
Higher-derivative terms in xPand
Dear all, I am using xPand to compute the tensor perturbations in a theory with higher derivatives.
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Higher-derivative terms in xPand
Dear all, I am using xPand to compute the tensor perturbations in a theory with higher derivatives.
Mar 21
Thomas Bäckdahl
Mar 20
Re: [xAct] Writing a function to calculate the post-Newtonian order
Hi! This depends a bit on how complicated expression you should be able to handle, but to handle some
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Re: [xAct] Writing a function to calculate the post-Newtonian order
Hi! This depends a bit on how complicated expression you should be able to handle, but to handle some
Mar 20
Rafael Carrasco Carmona
Mar 15
Lowering the indices of a variation
Hello, everyone I write this post because I have a problem when computing variations with 'xPert
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Lowering the indices of a variation
Hello, everyone I write this post because I have a problem when computing variations with 'xPert
Mar 15
Anupam Ah
,
Jose
2
Mar 14
define an operator which has distributive property
Hi, There are several ways to do this. A possibility is to use xTensor's internal tool to define
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define an operator which has distributive property
Hi, There are several ways to do this. A possibility is to use xTensor's internal tool to define
Mar 14
olse barn
,
TB
2
Mar 11
replacement rules
Hi! In general it is not a great idea to make rules that tries to replace several terms with
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replacement rules
Hi! In general it is not a great idea to make rules that tries to replace several terms with
Mar 11
olse barn
,
Thomas Bäckdahl
4
Mar 9
IndexCollect
thank you for your alternative proposal! Thomas Bäckdahl schrieb am Donnerstag, 9. März 2023 um 17:13
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IndexCollect
thank you for your alternative proposal! Thomas Bäckdahl schrieb am Donnerstag, 9. März 2023 um 17:13
Mar 9
Andrew
,
Thomas Bäckdahl
2
Mar 9
Problem with Solve conventions
Hi! This seems a bit annoying. Unfortunately Solve can do some random choices. To be sure that you
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Problem with Solve conventions
Hi! This seems a bit annoying. Unfortunately Solve can do some random choices. To be sure that you
Mar 9
Anupam Ah
, …
Jose
4
Mar 7
making a rule for converting from partial to covariant derivative
oh..this is great..thanks everyone.. this helps a lot On Wednesday, March 1, 2023 at 6:56:18 AM UTC+5
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making a rule for converting from partial to covariant derivative
oh..this is great..thanks everyone.. this helps a lot On Wednesday, March 1, 2023 at 6:56:18 AM UTC+5
Mar 7
Nitol Attar
,
Jose
3
Mar 5
MakeRule error
Hi Jose, Thank you for your feedback. Sorry for the late reply. I was traveling. Fortunately, I
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MakeRule error
Hi Jose, Thank you for your feedback. Sorry for the late reply. I was traveling. Fortunately, I
Mar 5
Naveen Kuntar
Mar 2
Holographic renormalisation of U(1) gauge field
Hello, How can we perform the holographic renormalisation of U(1) gauge field in the asymptotically
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Holographic renormalisation of U(1) gauge field
Hello, How can we perform the holographic renormalisation of U(1) gauge field in the asymptotically
Mar 2
Mikolaj Myszkowski
,
Jose
2
Feb 28
Reruning a mathematica notebook
Hi, This behavior is expected in all of xAct. Every symbol used must be defined with a unique type,
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Reruning a mathematica notebook
Hi, This behavior is expected in all of xAct. Every symbol used must be defined with a unique type,
Feb 28
Nitol Attar
,
Sergi Sirera-Lahoz
2
Feb 24
Integration by parts using VarD
Hi Nitol, I'm not sure how you wanted to use VarD to integrate by parts and discard total
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Integration by parts using VarD
Hi Nitol, I'm not sure how you wanted to use VarD to integrate by parts and discard total
Feb 24
Shubham Kumar Sinha
,
Jose
2
Feb 16
construct a specific second rank tensor
Hi, Yes, you can define tensor fields with indices in different vector spaces, like two tangent
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construct a specific second rank tensor
Hi, Yes, you can define tensor fields with indices in different vector spaces, like two tangent
Feb 16
Zakaria
, …
Jose
7
Feb 8
components of equations of motion using an ansatz ( for the metric and for Electromagnetic field) ( xTensor, xCoba)
Hi, There were three issues: 1) You were using a phi function without first declaring it with
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components of equations of motion using an ansatz ( for the metric and for Electromagnetic field) ( xTensor, xCoba)
Hi, There were three issues: 1) You were using a phi function without first declaring it with
Feb 8
Salva Mengual Sendra
,
Jose
2
Feb 8
Index order in xCoba
Hi, Answers inlined. On Wednesday, February 8, 2023 at 6:56:06 AM UTC-6 salvam...@hotmail.com wrote:
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Index order in xCoba
Hi, Answers inlined. On Wednesday, February 8, 2023 at 6:56:06 AM UTC-6 salvam...@hotmail.com wrote:
Feb 8
Max Banados
,
Jose
3
Jan 27
Keeping Head xTensor when defining objects in xCoba
Dear José, Thank you very much for your quick and informative reply. I agree that (error-free) tensor
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Keeping Head xTensor when defining objects in xCoba
Dear José, Thank you very much for your quick and informative reply. I agree that (error-free) tensor
Jan 27
Gregoire Mathys
,
Jose
2
Jan 27
Vary GR tensors with xpert, and obtain variation with respect to inverse metric
Hi, You are starting with the perturbation of Riemann[a, b, c, d], instead of the natural Riemann[-a,
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Vary GR tensors with xpert, and obtain variation with respect to inverse metric
Hi, You are starting with the perturbation of Riemann[a, b, c, d], instead of the natural Riemann[-a,
Jan 27
Kabouter9
,
Jose
2
Jan 27
Eigenvalues in xAct
Hi, This computation is too large for me to absorb and debug, but let me say this: You are calling
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Eigenvalues in xAct
Hi, This computation is too large for me to absorb and debug, but let me say this: You are calling
Jan 27
Andrew Kovachik
,
Jose
2
Jan 26
Why does MetricInBasis not define its own inverse rules
Hi again, This post is essentially equivalent to https://groups.google.com/g/xAct/c/zDHXAdP9Bp4?hl=en
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Why does MetricInBasis not define its own inverse rules
Hi again, This post is essentially equivalent to https://groups.google.com/g/xAct/c/zDHXAdP9Bp4?hl=en
Jan 26
Andrew Kovachik
,
Jose
2
Jan 26
Why does MetricInBasis not define rules for the inverse metric?
Hi, xCoba has two main modes of work: what I call the TensorValues framework and the CTensor
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Why does MetricInBasis not define rules for the inverse metric?
Hi, xCoba has two main modes of work: what I call the TensorValues framework and the CTensor
Jan 26
Nitol Attar
,
Jose
2
Jan 26
products in order and makerule
Hi, xTensor (and by extension of all xAct) works primarily with the Times product, which is
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products in order and makerule
Hi, xTensor (and by extension of all xAct) works primarily with the Times product, which is
Jan 26
alej...@gmail.com
,
Thomas Bäckdahl
7
Jan 26
About PrintAs and how to make customized operators look nice
Hi! Yes! For me too. I hope people find these posts useful to customize objects in xAct. Many thanks!
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About PrintAs and how to make customized operators look nice
Hi! Yes! For me too. I hope people find these posts useful to customize objects in xAct. Many thanks!
Jan 26
Giorgia Russo
,
Jose
3
Jan 19
How to speed up Einstein tensor computation
Thank you so much, it was really helpful! I guess I will have to deal with my little monster tensor
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How to speed up Einstein tensor computation
Thank you so much, it was really helpful! I guess I will have to deal with my little monster tensor
Jan 19
Ganesh Subramaniam
Jan 18
Type of spaces in xPand
Hi, Good day. I need a help in knowing what exactly the metric form that used in xPand packages, is
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Type of spaces in xPand
Hi, Good day. I need a help in knowing what exactly the metric form that used in xPand packages, is
Jan 18
Dong-han Yeom (염동한)
,
Markus B. Fröb
2
12/30/22
[FieldX] Inserting ansatz with vector bundle
Dear Dong-han, I'm not very familiar with xCoba, so I'm not sure if what I'm writing
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[FieldX] Inserting ansatz with vector bundle
Dear Dong-han, I'm not very familiar with xCoba, so I'm not sure if what I'm writing
12/30/22
james madison
, …
Jose
4
12/20/22
get einstein tensor for a metric with undetermined functions
Thank you. That makes sense. On Tuesday, December 20, 2022 at 9:06:13 AM UTC-6 Jose wrote: Hi, See
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get einstein tensor for a metric with undetermined functions
Thank you. That makes sense. On Tuesday, December 20, 2022 at 9:06:13 AM UTC-6 Jose wrote: Hi, See
12/20/22
Mre
,
Cyril Pitrou
2
12/4/22
Defining perturbed FLRW metric in Poisson gauge with xact
Hi, In that case I recommend to use the xPand package which goes on top of xTensor/xPert. It allows
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Defining perturbed FLRW metric in Poisson gauge with xact
Hi, In that case I recommend to use the xPand package which goes on top of xTensor/xPert. It allows
12/4/22
Ruben Campos Delgado
, …
Jose
5
11/28/22
xPert gives apparently the wrong answer
Hi Jose, ok I see, thank you very much. You use Perturbed[ ] which gives you the full expansion. I
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xPert gives apparently the wrong answer
Hi Jose, ok I see, thank you very much. You use Perturbed[ ] which gives you the full expansion. I
11/28/22
Jose
,
Falco
4
11/25/22
xAct livestream on November 23rd
Hi, Thanks. The notebook can be downloaded here: http://xact.es/xAct_RDLiveStream.nb Cheers, Jose. On
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xAct livestream on November 23rd
Hi, Thanks. The notebook can be downloaded here: http://xact.es/xAct_RDLiveStream.nb Cheers, Jose. On
11/25/22
Salva Mengual Sendra
,
Jose
2
11/15/22
Complex chart
Hi Salva, No, there is no explicit support for complex charts in xCoba. I think you would have to
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Complex chart
Hi Salva, No, there is no explicit support for complex charts in xCoba. I think you would have to
11/15/22
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