SynchronousGage perturbations of continuity equations

[Hengameh Bagherian]

Hello, 

I am brand new to xAct. I tried using xPand to write the continuity equation of the stress energy tensor in synchronous gauge, but I cannot get the results in terms of \eta and h which are the standard cosmological synchronous gauge variables. 

I am attaching my notebook here and any help would be appreciated. 

[Hengameh Bagherian]

P.S. 

Just to be clear, \eta and h are Fourier space scalar perturbations of the metric in synchronous gauge.

[Kay Lehnert]

Is this what you are looking for? The command VisualizeTensor[MyToxPand[MyCR[\[Nu]], "SynchronousGauge", 1], h] can do such a split (if this is what you need).

[Cyril Pitrou]

I think the easiest in that case is to postprocess the perturbations so as to use the variables of Ma&Bertschinger.

They are a bit annoying because of inverse Laplacians in their definitions.

See the example attached.

Best,

Cyril

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