ASKSAGE: Sage Q&A Forum - Latest question feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Fri, 04 Sep 2020 08:59:16 -0500Typo in Sagemanifolds worksheet ?https://ask.sagemath.org/question/53303/typo-in-sagemanifolds-worksheet/ Sorry to bother the group but I don't know how to report a technical (but inconsequential) typo in Kerr_Schild.ipynb
Where should I report it?
After In[33] or so, "Check of the Identity"
```
\frac{x^2 + y^2}{r^2 + a^2} + \frac{z^2}{r^2} = 1
```
Should be:
```
\frac{x^2 + y^2}{R^2 + a^2} + \frac{z^2}{R^2} = 1
```
It seems to be too trivial for a 'Ticket' on the Sagemanifolds forum. I am just reading the program in detail; checking my understanding.
rrogersFri, 04 Sep 2020 08:59:16 -0500https://ask.sagemath.org/question/53303/Source for Principal Null Directions Kerr, Example Worksheethttps://ask.sagemath.org/question/47468/source-for-principal-null-directions-kerr-example-worksheet/ In the Worksheet "Walker-Penrose Killing tensor in Kerr spacetime" of the SageManifolds project, the sheet gives the principal null directions for Kerr spacetime in Boyer-Lindquist coordinates. I have difficulties verifying (with Mathematica) that this is indeed the case and would appreciate a source. horropieTue, 13 Aug 2019 07:43:40 -0500https://ask.sagemath.org/question/47468/