Question: Any way to speed up computation in Physics package? Particularly define.

I am trying to define a Tensor expression in the physics package but it seems to be taking eons to do so, it has been running for quite some time but still no result to the point where I halt the computation. 

Does anyone have any ideas on how I could accelerate the process? 

I have attached the file I am working with. 

Define.mw

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