Group Cohomology

Examples of how cohomology arises, e.g. stability automorphisms that are not inner, Buzzard Selmer and Shafarevich group of a number field construction.

https://math.stackexchange.com/questions/312515/what-is-the-intuition-between-1-cocycles-group-cohomology

https://mathoverflow.net/questions/6950/why-is-the-standard-definition-of-cocycle-the-one-that-always-comes-up

http://www.math.columbia.edu/~bayer/S09/ModernAlgebra/semidirect.pdf

Sharafi's notes (see other notes too)

Fact that kernel of cocycle is subgroup... understand better?