ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Wed, 27 Jan 2021 18:48:55 +0100Extracting numerator of a Ricci tensor componenthttps://ask.sagemath.org/question/55479/extracting-numerator-of-a-ricci-tensor-component/ Hello
I'm solving Einstein equation in vacuum. I already computed the Ricci tensor. For example, de first Ricci component is saved in the following variable eq1:
eq1=EE[0,0]
The denominator of the component should vanish since since the other part of the equation is zero. How can I extract numerator of the expression. I have tried:
eq1.denominator()
But it does not work. Thanks
Omar MedbauWed, 27 Jan 2021 18:48:55 +0100https://ask.sagemath.org/question/55479/Sagemanifold - Connection components from a tensor (not a metric)https://ask.sagemath.org/question/44572/sagemanifold-connection-components-from-a-tensor-not-a-metric/ Dear community.
This might sound *dump*, but I'm trying to determine whether a tensor satisfy the properties of a metric (under certain conditions). Of course it is a (0,2)-symmetric tensor, call it $S$, but I cannot (to my understanding) calculate the (Levi-Civita-like) connection components that would be associated to $S$... unless I declare it as a metric.
The way it is implemented makes sense... and it's solid!
## What I did...?
I defined like a metric and calculate the associated connection (and curvatures)
## Why should I do something else?
In the file `src/sage/manifolds/differentiable/metric.py` the metric is defined (as it should) to be symmetric, but it does not allow to consider extensions of General Relativity like say Einstein--Strauss model. Thus, I need an instance to calculate the *derived quantities* of a tensor that is a generalization of a metric.
### Question:
**Is this possible?**DoxTue, 04 Dec 2018 09:18:37 +0100https://ask.sagemath.org/question/44572/