---
title: "Sterk91"
aliases: ["Sterk91"]
annotation-target: Ster91.pdf
flashcard: "Reading::Unsorted"
created: 2023-03-26T11:58
updated: 2023-03-31T11:33
---

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# Sterk91

- [x] What is $I_m(\Lambda)$? ✅ 2023-03-30
	- [ ] The space of primitive rank $m$ isotropic sublattices.
- [x] What is $\Orth^*(\Lambda)$? ✅ 2023-03-30
	- [ ] $\ts{g\in \Orth(\Lambda) \st g^* = \id}$ where $g^*: D(\Lambda)\selfmap$ is induced.
- [x] What is the Enriques lattice? ✅ 2023-03-30
	- [ ] $M \da H \perp E_8(-1)$.
- [ ] What is a nodal Enriques surface?
- [x] Describe Vinberg's algorithm. ✅ 2023-03-31
	- [ ] Take a vector $x\in C \intersect N$
	- [ ] Look for hyperplanes $H_i = e_i^\perp$ where $s_{e_i} \in W(G)$ such that 
	- [ ] $H_1$ is closed to $x$ in $\Lambda(N)$, i.e. $y=e_1$ minimizes $(xy)^2 / \norm{y^2}$.
	- [ ] $e_2$ is such that $e_1 e_2 \geq 0$ and $H_2$ is closed to $x$ under these conditions, etc.