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xAct Tensor Computer Algebra
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xAct Tensor Computer Algebra
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Petar
, …
Thomas Bäckdahl
7
Jun 5
ToCanonical is very slow
Hi again! I tried another thing. You can modify the order the tensors are sorted before
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ToCanonical is very slow
Hi again! I tried another thing. You can modify the order the tensors are sorted before
Jun 5
Ефим
Jun 5
Help!
my question is why after that i have defined my metric, i will get the contravariant and covariant
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Help!
my question is why after that i have defined my metric, i will get the contravariant and covariant
Jun 5
. Davidson Noby Joseph
,
Alfonso García-Parrado Gómez-Lobo
3
Jun 1
ToCannonical/ Grouping of 2 forms in 4 D
Hi Alfonso, Thank you for your swift reply! Thank you for your comment on dx and using dX. I managed
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ToCannonical/ Grouping of 2 forms in 4 D
Hi Alfonso, Thank you for your swift reply! Thank you for your comment on dx and using dX. I managed
Jun 1
olse barn
,
Jose
2
May 25
vanishing of expressions
Hi, ToCanonical is the function to check whether an expression is 0. There are two comments to make
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vanishing of expressions
Hi, ToCanonical is the function to check whether an expression is 0. There are two comments to make
May 25
Anupam Ah
,
Jose
4
May 19
Raise and lower indices in xTensor
Yes, we have the function SeparateMetric for that. It will make explicit all metric contractions. Try
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Raise and lower indices in xTensor
Yes, we have the function SeparateMetric for that. It will make explicit all metric contractions. Try
May 19
Maryna М
, …
Jose
3
May 18
Variations wrt CMetric
Hi, The CTensor and TensorValues approaches are alternative and complementary. Each one has
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Variations wrt CMetric
Hi, The CTensor and TensorValues approaches are alternative and complementary. Each one has
May 18
thomas1...@gmail.com
May 17
New package : Trace decomposition, Irreducible decomposition and symplectic manifold
Hi everyone, I would like to anounce the release of a new package called xBrauer. This package allows
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New package : Trace decomposition, Irreducible decomposition and symplectic manifold
Hi everyone, I would like to anounce the release of a new package called xBrauer. This package allows
May 17
Maryna М
,
Jose
2
May 14
CTensor contraction
Hi, There are a few issues here: 1) With symbolic components, SetCMetric cannot compute the sign of
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CTensor contraction
Hi, There are a few issues here: 1) With symbolic components, SetCMetric cannot compute the sign of
May 14
Harry Ye
,
Thomas Bäckdahl
2
May 14
Setting covariant derivatives to ordinary (partial) derivatives
Hi! This is not how patterns work in Mathematica. Read the help in Mathematica. For instance "
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Setting covariant derivatives to ordinary (partial) derivatives
Hi! This is not how patterns work in Mathematica. Read the help in Mathematica. For instance "
May 14
Alejandro Muñoz Ovalle
,
Jose
2
May 10
Fluctuation of a sub-metric
Hi, If I understand correctly you have a background metric that can be decomposed as 1+4 by diagonal
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Fluctuation of a sub-metric
Hi, If I understand correctly you have a background metric that can be decomposed as 1+4 by diagonal
May 10
matteo....@le.infn.it
,
Jose
2
May 10
contraction with epsilon tensor using CTensor framework
Hi, You can compute the epsilon tensor of met with epsilon[met]. Then you can compute contractions
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contraction with epsilon tensor using CTensor framework
Hi, You can compute the epsilon tensor of met with epsilon[met]. Then you can compute contractions
May 10
Harry Ye
,
Cyril Pitrou
2
Apr 19
Set certain perturbations to zero
Hi, First you can use the option BackgroundFieldMethod = True to turn off all second order
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Set certain perturbations to zero
Hi, First you can use the option BackgroundFieldMethod = True to turn off all second order
Apr 19
Rafael Carrasco Carmona
,
Jose
2
Apr 18
Lowering the indices of a variation
Hi, Can you provide a complete set of inputs (or even better a small notebook) where we can see an
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Lowering the indices of a variation
Hi, Can you provide a complete set of inputs (or even better a small notebook) where we can see an
Apr 18
Prit
,
Jose
2
Apr 18
installation difficulties (Mathematica 11.0, Windows 11)
Hi, Do you get the path to xTensor.m when you evaluate this line? FileNames[FileNameJoin[{$
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installation difficulties (Mathematica 11.0, Windows 11)
Hi, Do you get the path to xTensor.m when you evaluate this line? FileNames[FileNameJoin[{$
Apr 18
Nancy Lemon
,
Jose
2
Apr 18
How to avoid Ricci tensors in perturbative expansion of the curvature scalar and the Einstein tensor?
Hi, I don't think I understand this question. The perturbation of RiemannCD[-a, -b, -c, d] is
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How to avoid Ricci tensors in perturbative expansion of the curvature scalar and the Einstein tensor?
Hi, I don't think I understand this question. The perturbation of RiemannCD[-a, -b, -c, d] is
Apr 18
Debojyoti Mondal
Mar 30
Deriving metric from action
Hi There, I am trying to derive equation 7 and 8 using equations 1-6 in the attached file. I am
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Deriving metric from action
Hi There, I am trying to derive equation 7 and 8 using equations 1-6 in the attached file. I am
Mar 30
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
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
unread,
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
unread,
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,
unread,
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
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