Hello, everyone
I write this post because I have a problem when computing variations with 'xPert'. My problem is that I need to compute a variation of a tensor which can be always expressed as something proportional to the variation of the metric. The problem that I found is that Mathematica gives me one term proportional to \Delta g^{\mu\nu} and another to \Delta g_{\mu\nu}. In order to write everything in terms of the latter term I added an automatic rule as follows:
AutomaticRules[g, MakeRule[{Perturbation[g[\[Mu], \[Nu]],1], -g[\[Mu], \[Alpha]] g[\[Nu], \[Beta]] Perturbation[ g[-\[Alpha], -\[Beta]], 1]}]]
However, this line does not solve the problem, since it also changes the sign of Perturbation[g[\[Mu],\[Nu]],1]. Do you know any way to fix this? Thank you so much in advance.
Kind regards,
Rafa.