Tetrad formalism

[Diego Fernando López Restrepo]

Has xAct something about tetrad formalism?, case if, How can I define a tetrad field?

[Thomas Bäckdahl]

Hi!

There are several possibilities. Everything depends on what you want to do and which tetrad/frame formalism you would like to use.

There is an old file in the Documentation folder called PublicNPGHP.nb that contains some ideas on how to calculate with NP or GHP formalism for 1+3 dimensional spin manifolds. There is also a new package SpinFrames that does most of the things in PublicNPGHP.nb notebook for you. Unfortunately I have not had time to write a proper documentation file for it, but there is the SpinFramesExamples.nb file. You can see all functions in the package by typing ?xAct`SpinFrames`*
If you have tensor expressions and want to formulate them in NP or GHP formalism, I would recommend that you translate them to spinors first and then use ToNP or ToGHP, possibly followed by DyadComponents.

For simpler frame formalisms you can probably use xCoba.

Take a look at these and tell us more specifically what you would like to do. Do you want to do abstract calculations or calculations for a specific metric?

Regards

Thomas

2016-04-18 18:49 GMT+02:00 Diego Fernando López Restrepo <difel...@gmail.com>:

Has xAct something about tetrad formalism?, case if, How can I define a tetrad field?

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