Soft introduction to cohomology

Pythagorean triple and Hilbert theorem 90

http://www.math.harvard.edu/~elkies/Misc/hilbert.pdf

 

 

17 wallpaper groups

 

 

http://golem.ph.utexas.edu/category/2012/06/cohomology_in_everyday_life.html

 

==carrying and cocycles

• http://terrytao.wordpress.com/2011/06/07/central-extensions-of-lie-groups-and-cocycle-averaging/
• http://blog.mikael.johanssons.org/archive/2006/07/carry-bits-and-group-cohomology/
• http://www.physicsforums.com/showthread.php?t=182195
• Isaksen, Daniel C. 2002. “A Cohomological Viewpoint on Elementary School Arithmetic”. The American Mathematical Monthly 109 (9) (11월 1): 796-805. doi:10.2307/3072368. http://www.jstor.org/stable/3072368