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xAct Tensor Computer Algebra
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xAct Tensor Computer Algebra
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Bhaskar Shukla
, …
Armando Roque
5
Mar 18
Varying Einstein-Hilbert action through xAct
Dear Armando, Thanks a lot for rectifying my mistake and providing an additional illustrative
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Varying Einstein-Hilbert action through xAct
Dear Armando, Thanks a lot for rectifying my mistake and providing an additional illustrative
Mar 18
Omar Z
,
Thomas Bäckdahl
3
Mar 18
Print an Inert Head with additional labels
Thank you very much, your help is very appreciated. Omar On Monday, March 18, 2024 at 12:52:38 PM UTC
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Print an Inert Head with additional labels
Thank you very much, your help is very appreciated. Omar On Monday, March 18, 2024 at 12:52:38 PM UTC
Mar 18
Claire
,
Jose
2
Mar 18
Equations of motion for a given chart
Hi, Your notebook is quite large and I haven't looked at all computations. I evaluated it and see
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Equations of motion for a given chart
Hi, Your notebook is quite large and I haven't looked at all computations. I evaluated it and see
Mar 18
Joaquín Itu
,
Jose
2
Mar 18
Memory usage ramps up until crash
Hi, Your expressions are very large, and I doubt they can be simplified. I reattach your notebook
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Memory usage ramps up until crash
Hi, Your expressions are very large, and I doubt they can be simplified. I reattach your notebook
Mar 18
Biel Cardona Rotger
,
Jose
2
Mar 18
Proper way to deal with flat indices
Hi, A first important comment is that xTensor never contracts metrics automatically. If we have a
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Proper way to deal with flat indices
Hi, A first important comment is that xTensor never contracts metrics automatically. If we have a
Mar 18
alej...@gmail.com
,
Jose
2
Mar 18
Charts with common coordinates
Hi, When a chart is defined, an upvalue like this is attached to each scalar field of the chart,
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Charts with common coordinates
Hi, When a chart is defined, an upvalue like this is attached to each scalar field of the chart,
Mar 18
Sashwat Tanay
,
Jose
2
Mar 18
Covariant derivative with tetrads
Hi, The expression cd[-a][ x[{b, fred}] ] is the covariant derivative cd[-a] of x[{b, fred}] == x[a]
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Covariant derivative with tetrads
Hi, The expression cd[-a][ x[{b, fred}] ] is the covariant derivative cd[-a] of x[{b, fred}] == x[a]
Mar 18
Jose
2
Mar 14
xAct is 20 years old today!
Hi again! The event celebrating the 20 years of xAct will be next week, Friday March 22nd at 10am,
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xAct is 20 years old today!
Hi again! The event celebrating the 20 years of xAct will be next week, Friday March 22nd at 10am,
Mar 14
Prosenjit Paul
,
TB
3
Mar 12
xTensor
Thank You. On Tuesday 12 March 2024 at 13:14:19 UTC+5:30 TB wrote: Hi! You have probably set up
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xTensor
Thank You. On Tuesday 12 March 2024 at 13:14:19 UTC+5:30 TB wrote: Hi! You have probably set up
Mar 12
Debojyoti Mondal
,
Jose
3
Mar 1
Black hole in f(Q,T) gravity
Thank you for the reply and the edits you made. Ptensor, Qtensor and SE are P[-a,-b,-c], Q[-a,-b,-c]
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Black hole in f(Q,T) gravity
Thank you for the reply and the edits you made. Ptensor, Qtensor and SE are P[-a,-b,-c], Q[-a,-b,-c]
Mar 1
John Conrad
,
Jose
2
Feb 28
Specifying components of metric tensor then getting inverse
Hi, There is currently no automated way in xAct to compute the inverse of an object like this. For
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Specifying components of metric tensor then getting inverse
Hi, There is currently no automated way in xAct to compute the inverse of an object like this. For
Feb 28
PUSHPARAJ CHAKRAVARTI
,
Jose
2
Feb 28
Can't find the Invar database.
Hi, First, note that you need <<xAct`Invar` but you use <<xAct`Invar' The final quote
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Can't find the Invar database.
Hi, First, note that you need <<xAct`Invar` but you use <<xAct`Invar' The final quote
Feb 28
PUSHPARAJ CHAKRAVARTI
, …
Thomas Bäckdahl
5
Feb 28
xTensor compatiblity for Metric contraction
Hi! If something gives errors please provide a small example notebook where this is visible. Without
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xTensor compatiblity for Metric contraction
Hi! If something gives errors please provide a small example notebook where this is visible. Without
Feb 28
William Emond
,
Jose
2
Feb 24
How do I avoid repeated dummy indices in recursive sum
Hi, Note that you have something like g[k, l] (J[-m, -k] // ReplaceDummies) The function
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How do I avoid repeated dummy indices in recursive sum
Hi, Note that you have something like g[k, l] (J[-m, -k] // ReplaceDummies) The function
Feb 24
Nitol Attar
Feb 20
xPert for metric parametrization
Hi all, Is it possible to use xPert for a Kaluza-Klein decomposition of the metric g[mu,nu]? Any
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xPert for metric parametrization
Hi all, Is it possible to use xPert for a Kaluza-Klein decomposition of the metric g[mu,nu]? Any
Feb 20
Kivanc İbrahim Ünlütürk
,
Jose
2
Feb 19
Covariant derivatives computed as partial derivatives when computed in a coordinate chart
Hi, This is a common confusion, due to the way the CD derivatives and the basis components are
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Covariant derivatives computed as partial derivatives when computed in a coordinate chart
Hi, This is a common confusion, due to the way the CD derivatives and the basis components are
Feb 19
Debojyoti Mondal
Feb 16
f(Q,T) gravity
Hi, I am trying to define weyl cartan connection and non metricity tensor and trace of stress energy
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f(Q,T) gravity
Hi, I am trying to define weyl cartan connection and non metricity tensor and trace of stress energy
Feb 16
Joel Feske
,
Jose
2
Feb 7
Helmholtz decomposition
Hi, No, there is no special support for this type of computation in xAct. I'd recommend to have a
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Helmholtz decomposition
Hi, No, there is no special support for this type of computation in xAct. I'd recommend to have a
Feb 7
Carmen López Jurado
,
Jose
2
Feb 7
xCoba - how to save a C tensor in a file and load it in other notebooks
Hi, I'm afraid there is not enough information to know what the problem may be. Saving and
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xCoba - how to save a C tensor in a file and load it in other notebooks
Hi, I'm afraid there is not enough information to know what the problem may be. Saving and
Feb 7
Saul Teukolsky
, …
Mehmet Kemal Gümüş
4
Jan 25
xAct broken in recent intel/linux systems?
I tried this commands but the xPerm gives another error: "LinkOpen::linke: Could not find
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xAct broken in recent intel/linux systems?
I tried this commands but the xPerm gives another error: "LinkOpen::linke: Could not find
Jan 25
Andrew Kovachik
,
Jose
3
Jan 22
How to contract these basis elements or prevent their appearance?
I see thank you Jose! I think the lack of PDcoords is really an error in my MWE. It looks like in my
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How to contract these basis elements or prevent their appearance?
I see thank you Jose! I think the lack of PDcoords is really an error in my MWE. It looks like in my
Jan 22
Sharang Iyer
Jan 18
Defining a product metric and defining normal to a hypersurface
Hi, I am new to abstract computation in xAct. I am trying to define a metric of the form: ds^2 = -2 r
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Defining a product metric and defining normal to a hypersurface
Hi, I am new to abstract computation in xAct. I am trying to define a metric of the form: ds^2 = -2 r
Jan 18
Gustav
,
Jose
2
Jan 15
Calculating Lie derivatives in a chart
Hi Gustav, Indeed, it should be possible to perform this computation in both ways you mention. As you
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Calculating Lie derivatives in a chart
Hi Gustav, Indeed, it should be possible to perform this computation in both ways you mention. As you
Jan 15
Rajalakshmi S
,
Jose
6
Jan 15
Defining arbitrary function of scalar fields (coordinates) in metric
Hi again, You have a metric with six free functions. Therefore the curvature tensors will not be
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Defining arbitrary function of scalar fields (coordinates) in metric
Hi again, You have a metric with six free functions. Therefore the curvature tensors will not be
Jan 15
Pavan Dharanipragada
,
Jose
7
Jan 9
xPert, perturbation of expressions involving perturbation parameter
Thank you so much, Jose. I love xAct and this forum! Pavan On Tuesday 9 January 2024 at 00:51:50 UTC+
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xPert, perturbation of expressions involving perturbation parameter
Thank you so much, Jose. I love xAct and this forum! Pavan On Tuesday 9 January 2024 at 00:51:50 UTC+
Jan 9
Safinaz Salem
,
Jose
3
Jan 6
Finding the perturbation of a scalar field
Thanks very much for your answer. Safinaz On Wednesday 3 January 2024 at 16:09:00 UTC+2 Jose wrote:
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Finding the perturbation of a scalar field
Thanks very much for your answer. Safinaz On Wednesday 3 January 2024 at 16:09:00 UTC+2 Jose wrote:
Jan 6
José Ferreira
,
Jose
3
Jan 3
Idiomatic way of getting CTensor from computations in xCoba
Works great, many thanks. On Wednesday, January 3, 2024 at 1:45:45 PM UTC Jose wrote: Hi, What you
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Idiomatic way of getting CTensor from computations in xCoba
Works great, many thanks. On Wednesday, January 3, 2024 at 1:45:45 PM UTC Jose wrote: Hi, What you
Jan 3
Brian Beckman
,
Jose
3
Jan 2
Differences with documentation?
Ah, thanks! On Thursday, December 28, 2023 at 2:09:35 PM UTC-8 Jose wrote: Hi, The documentation
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Differences with documentation?
Ah, thanks! On Thursday, December 28, 2023 at 2:09:35 PM UTC-8 Jose wrote: Hi, The documentation
Jan 2
Sashwat Tanay
,
Jose
2
12/28/23
Most efficient way to show that something equals 0
Hi, There is no unique answer to your questions. Different strategies of simplification may be more
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Most efficient way to show that something equals 0
Hi, There is no unique answer to your questions. Different strategies of simplification may be more
12/28/23
Madhu Mishra
,
Jose
2
12/28/23
Notations not appearing in the output
Hi, It seems you have something configured globally in your system to return outputs in
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Notations not appearing in the output
Hi, It seems you have something configured globally in your system to return outputs in
12/28/23