10.38.3 Can you answer these questions?

10.38.3.1 Why does Gather behaves this way?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=308544

I wrote the following: 
 Z = {{1, 3}, {3, 2}, {4, 1}, {2, 4}}; 
Gather[Z, IntersectingQ[#1, #2] &] 
 
This yields: 
... 
[gathering]
 

asked by Red Banana https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=603 Score of 1

10.38.3.2 How to Substitute a Metric into a Variation of the Action in Mathematica to Obtain Field Equations?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=308457

I have already calculated the variation of an action for a modified gravitational theory, and now I want to substitute a specific metric (e.g., the Schwarzschild metric) into this variation in ... 
[mathematical-optimization] [replacement] [algebraic-manipulation] [tensors]
 

asked by Elena Margalejo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=103650 Score of 1

10.38.3.3 Is there a way to give an analytical result to the following integral?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=308475

I hope to obtain the analytical result of  gg[r] . Is there a way to give an analytical result to the following integral of function ... 
[differential-equations] [calculus-and-analysis]
 

asked by little star https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=81586 Score of 2

answered by Craig Carter https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=12461 Score of 0