Bourbaki

Exercise 13, § 4

Tag 0AYX, permanent. Cite it as [Bourbaki, Tag 0AYX].

Lie Groups and Lie Algebras, VI

Let V be the hyperplane in R9\mathbf{R}^9 with equation x1+⋯+x9=0x_1 + \cdots + x_9 = 0. Let R be the subset of V consisting of the points

(2,2,2,−1,−1,−1,−1,−1,−1),(−2,−2,−2,1,1,1,1,1,1), (2, 2, 2, -1, -1, -1, -1, -1, -1), \quad (-2, -2, -2, 1, 1, 1, 1, 1, 1),
(3,−3,0,0,0,0,0,0,0) (3, -3, 0, 0, 0, 0, 0, 0, 0)

together with the points obtained from these by permuting the coordinates. Show that R is a root system in V of type E8E_8.

Solution

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Cites

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Transcribed from the printed volume. Not translated.