One way the characterize certain classes of -groups is via exact sequences
-group | ||||
---|---|---|---|---|
formal k-group? | connected? | étale | p.34 | |
finite k-group? | infinitesimal? | étale | splits if is perfect | p.35 |
affine k-group? | multiplicative | smooth? | is infinitesimal |
(p. 39)
If is perfect any finite affine -group is in a unique way the product of four subgroups
where
is a formal étale multiplicative group.
is a formal étale unipotent group.
is a formal infinitesimal multiplicative group.
is a infinitesimal unipotent group.
affine commutative -group | is affine commutative formal -group | p.27 |
finite commutative -group | finite commutative -group | p.27 |
constant -group | diagonalizable -group | p.36 |
étale k-group | multiplicative k-group | p.37 |
multiplicative k-group | is étale formal -group | p.37 |
unipotent k-group | connected formal group | p.38 |
Let be a field, let be the separable clusure of , let denote the algebraic closure of .
multiplicative | diagonalizable | diagonalizable | diagonalizable | p.38 |
étale | constant | constant | p.17 |
unipotent | multiplicative | étale | connected | infinitesimal | diagonalizable | p-divisible | |
unipotent | |||||||
multiplicative | |||||||
étale | |||||||
connected | |||||||
infinitesimal | |||||||
diagonalizable | |||||||
p-divisible | and A(p) |