Combining xTensor with xCoba to get explicit equations of motion

[Héloïse]

Hi everyone,

I am considering a specific class of scalar-tensor Horndeski theories. I have obtained the equations of motion in tensorial form with xTensor, and would now like to evaluate them explicitly for a given diagonal metric in a given set of coordinates with xCoba.

I have followed two different approaches to do so, but both "fail":

1) In Approach1.nb (see attached), some tensorial expressions remain after evaluating it (like Christoffel symbols and basis vectors). What am I doing wrong here?

2) In Approach2.nb (see attached), the evaluation is just taking so long that I have to abort and do no know whether this approach is working or not. Is this approach correct? If yes, can I do some further simplifications to make the calculation faster?

More generally, I am looking for a standardised framework to combine xTensor with xCoba for such calculations, something I have not found in xAct documentation.

Thank you in advance for your detailed help!

Best,

Héloïse