Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 66

for questions about deformation theory, including deformations of manifolds, schemes, Galois representations, and von Neumann algebras.

9 votes

Deformation theory of representations of an algebraic group

Here's not a complete answer, but I think an enlightening trick. Deformations of V over the dual numbers are always in bijection with Ext1(V,V) in any abelian category. The trick is that if you have …
Ben Webster's user avatar
  • 44.7k
4 votes

algebraic group G vs. algebraic stack BG

If G is a group scheme over k (algebraic closed), then let me talk through how to get G back by looking at the stack BG. The k points of BG (which is a groupoid) consist of one point whose automorphi …
Ben Webster's user avatar
  • 44.7k
19 votes

Deformations of semisimple Lie algebras

While I think that what Johannes wrote is right, it misses out on an underlying principle. There's a one sentence explanation for this fact, which is "the tangent space to a Lie algebra in the moduli …
Ben Webster's user avatar
  • 44.7k