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Algebraic varieties with group operations given by morphisms, or group objects in the category of algebraic varieties, the category of algebraic schemes, or closely related categories.

12 votes
3 answers
1k views

Is the Gelfand-Graev character isomorphic to a cohomology group for some sheaf on a Deligne-...

Deligne-Lusztig theory is awesome. You take a maximal torus $T$, you take a character $\theta$, construct a variety $X_T$$^*$, take etale cohomology, get a virtual character $R_T^\theta$, maybe it's …
Dror Speiser's user avatar
  • 4,593
9 votes
1 answer
444 views

Are affine groups over rings of integers finitely generated?

I'll begin by saying that I'm not sure what I want to ask specifically, but pretty sure what in general, so please don't hold my misunderstandings against me, but do comment on them. I know that the …
Dror Speiser's user avatar
  • 4,593
6 votes
1 answer
336 views

Finite field analogue of representations in same packet have equal central character

In Kevin Buzzard's recent question, a warm up question was: if two automorphic representations are nearly equivalent, then are the central characters of their local components equal? Working my way u …
Dror Speiser's user avatar
  • 4,593
3 votes
1 answer
246 views

Is this unipotent group, over characteristic 2, connected?

Let $E_{ij}(x)\in \mathrm{Mat}_{7\times7}(\overline{\mathbb{F}}_2)$ be the matrix with zeros everywhere, except for the value $x$ at $ij$. Set $$a(x)=1+E_{12}(x)+E_{34}(x)+E_{56}(x),\quad b(y)=1+E_{23 …
Dror Speiser's user avatar
  • 4,593
3 votes
1 answer
531 views

Points on Deligne-Lusztig varieties: Interpreting Borels in relative position as flags with ...

Background I am studying the paper "On the Green polynomials of classical groups" by Lusztig, in which he computes the values of the Deligne-Lusztig representation, corresponding to a Coxeter element …
Dror Speiser's user avatar
  • 4,593