Computation is zero in one way but non zero in the other

[Sebastian Bahamonde]

I am having a weird problem that I have been stuck for some hours:

1) I computed an expression given by FieldEqConnectionTermino1A

2) I copied the correct Eq in FieldEqConnectionTermino1ACorrect

If I subtracted them, I am not getting zero.

However, if :

 I create a rule usingFieldEqConnectionTermino1A and subtract it with FieldEqConnectionTermino1ACorrect, it says that is correct (zero). 

So, this is very weird, is it a bug? does anyone know where is the problem?

I am attaching my Mathematica file here.

Thanks.

[Jose]

Hi,

You are working with partial derivatives of the metric, for which some operations of raising and lowering indices cannot be performed. You are also loading xTras, which loads xPert, which changes the default settings of metric contraction to be more permissive in ToCanonical and MetricRule. I see you already undo some of this with

   SetOptions[ToCanonical, UseMetricOnVBundle -> None]

You should also do

   SetOptions[MakeRule, {MetricOn -> None, ContractMetrics -> False}]

Repeat the computations with these settings, and I expect things will work better. Try to use each individual tensor always with its canonical configuration of indices. When working with partial derivatives and metric factors, canonicalization gets a lot more complicated because partial derivatives of the metric need to be added if indices are not in their original positions.

I realize that this combination (partial derivatives of the metric + xTras/xPert + MakeRule) is dangerous and there should be some warnings about it, like there are in ToCanonical.

Cheers,

Jose.