ASKSAGE: Sage Q&A Forum - Latest question feedhttp://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Fri, 16 Aug 2019 02:29:54 -0500cosmological spacetimeshttp://ask.sagemath.org/question/47496/cosmological-spacetimes/ Hi,
I need an example on how to perform the Einstein Field Equations for a universe which is anisotropic and where the clustering of masses are aligned to an arbitrary axis (axial pole).
Just like the example given for Friedmann equations in the sagemanifolds examples website.
ThanksvickFri, 16 Aug 2019 02:29:54 -0500http://ask.sagemath.org/question/47496/Sagemanifold - Connection components from a tensor (not a metric)http://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 02:18:37 -0600http://ask.sagemath.org/question/44572/