On the classification of simple Lie algebras of dimension seven over fields of characteristic 2

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On the classification of simple Lie algebras of dimension seven over fields of characteristic 2 Alexander Grishkov1,2 · Marinês Guerreiro3 · Wilian Francisco de Araujo4

© Instituto de Matemática e Estatística da Universidade de São Paulo 2020

Abstract This paper is the second part of paper (Grishkov and Guerreiro in São Paulo J Math Sci v4(1):93–107, 2010) about simple 7-dimensional Lie algebras over an algebraically closed field k of characteristic two. In this paper we prove that all simple 7-dimensional Lie algebras over k of absolute toral rank three are isomorphic to the Cartan algebra W1 or the Hamilton algebra H2 . We hope to prove that those algebras are the unique simple 7-dimensional Lie algebras over the field k. Observe that in the case of absolute toral rank 2 this fact was proved in [2]. Keywords  Simple Lie algebra · Toral subalgebra · Absolute toral rank

Communicated by Vyacheslav Futorny. A. Grishkov: Supported by FAPESP and CNPq Processo 307824/2016-0, Brazil and RFBR, Grant 16-01-00577a, Russian. M. Guerreiro: Supported by FAPESP Processo N. 04/07774-2, Brazil. * Alexander Grishkov [email protected] Marinês Guerreiro [email protected] Wilian Francisco de Araujo [email protected] 1

Instituto de Matemática e Estatística, Universidade de São Paulo Rua do Matão 1010, São Paulo CEP 05508‑090, Brazil

2

Omsk State University, n.a. F.M.Dostoevskii pr. Mira 55‑A, Omsk, Russia 644077

3

Departamento de Matemática, Centro de Ciências Exatas e Tecnológicas, Universidade Federal de Viçosa, Viçosa, M.G., Brazil

4

Universidade Tecnológica Federal do Paraná, R. Cristo Rei, Vila Becker, Toledo, PR, Brazil



13

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São Paulo Journal of Mathematical Sciences

1 Introduction The classification of simple finite dimensional Lie algebras over an algebraically closed field k of characteristic two is not finished until now. The first case when we have not yet the classification of the simple n-dimensional Lie algebras over k is the case n = 7 . We know two simple 7-dimensional Lie algebras over k, the Cartan algebra W1 and the Hamilton algebra H2 . Recall the definition of those algebras from [2]. In the two following tables we give the multiplication of the 2-closure W of the Witt–Zassenhaus algebra W1 and the 2-closure H of the Hamilton algebra H2 . 𝜂

𝜅

𝜅

y−1

y0

y1

y2

y3

y4

y5

𝜂

0

y4

y2

y5

0

0

0

0

0

0

𝜅

y4

𝜅

0

0

0

y−1

y0

y1

y2

y3

𝜅 [2]

y2

0

0

0

0

0

0

y−1

y0

y1

y−1

y5

0

0

𝜅

y−1

y0

y1

y2

y3

y4

y0

0

0

0

y−1

y0

y1

0

y3

0

y5

y1

0

y−1

0

y0

y1

y2

0

y4

y5

0

y2

0

y0

0

y1

0

0

0

y5

0

0

y3

0

y1

y−1

y2

y3

y4

y5

𝜂

0

0

y4

0

y2

y0

y3

0

y5

0

0

0

0

y5

0

y3

y1

y4

y5

0

0

0

0

0

Table of multiplication of the 2-closure W of W1. In this table the last seven elements form a basis of the simple Lie algebra W1 . t

m

n

V0

V1

E1

E0

F0

G

t

t

0

0

V0

V1

0

0

m

0

0

E0

0

0

0

0

F1

F0

0

V1

V0

n

0

E0

0

0

F1

G

0

E1

0

0

0

V0

V0

0

0

0

0

V1

V1

V1

0

F1

0

m