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3 votes
0 answers
128 views

Smooth unipotent algebraic groups over $\mathbb A^n$

Let $G\to \mathbb A^n_{\mathbb C}$ be a smooth morphism whose fibers at any point of $\mathbb A^n$ are unipotent groups. Can we conclude that $G\simeq \mathbb A^{n+N}_{\mathbb C}$ for some $N$, as a ...
W.Rether's user avatar
  • 455
4 votes
0 answers
325 views

In which sense affine Grassmannian is "affine"

A pretty naïve question: Which meaning has the term "affine" in the notion of affine Grassmanian. Especially, I do not see any immediate connection to the concept of an "affine scheme&...
user267839's user avatar
  • 5,998
7 votes
1 answer
229 views

Homological contractibility of a prestack

This question is in reference to Gaitsgory's preprint Contractibility of the space of rational maps. On p. 5 of the preprint, Gaitsgory defines a prestack $\mathscr{Y}$ (say over affine $\mathbb{C}$-...
Tyler Foster's user avatar
11 votes
3 answers
1k views

The affine Grassmannian and the Bogomolny equations

In "Electric-Magnetic Duality and The Geometric Langlands Program", Sections 9 and 10, Kapustin and Witten describe certain convolution varieties in the affine Grassmannian (and more ...
Ben Webster's user avatar
  • 44.7k