Group theory → Lie groups Lie groups |
---|
![]() |
This article gives a table of some common Lie groups and their associated Lie algebras.
The following are noted: the topological properties of the group (dimension; connectedness; compactness; the nature of the fundamental group; and whether or not they are simply connected) as well as on their algebraic properties (abelian; simple; semisimple).
For more examples of Lie groups and other related topics see the list of simple Lie groups; the Bianchi classification of groups of up to three dimensions; see classification of low-dimensional real Lie algebras for up to four dimensions; and the list of Lie group topics.
Column legend
Lie group | Description | Cpt | UC | Remarks | Lie algebra | dim/R | ||
---|---|---|---|---|---|---|---|---|
Rn | Euclidean space with addition | N | 0 | 0 | abelian | Rn | n | |
R× | nonzero real numbers with multiplication | N | Z2 | – | abelian | R | 1 | |
R+ | positive real numbers with multiplication | N | 0 | 0 | abelian | R | 1 | |
S1 = U(1) | the circle group: complex numbers of absolute value 1 with multiplication; | Y | 0 | Z | R | abelian, isomorphic to SO(2), Spin(2), and R/Z | R | 1 |
Aff(1) | invertible affine transformations from R to R. | N | Z2 | – | solvable, semidirect product of R+ and R× | 2 | ||
H× | non-zero quaternions with multiplication | N | 0 | 0 | H | 4 | ||
S3 = Sp(1) | quaternions of absolute value 1 with multiplication; topologically a 3-sphere | Y | 0 | 0 | isomorphic to SU(2) and to Spin(3); double cover of SO(3) | Im(H) | 3 | |
GL(n,R) | general linear group: invertible n×n real matrices | N | Z2 | – | M(n,R) | n2 | ||
GL+(n,R) | n×n real matrices with positive determinant | N | 0 | Z n=2 Z2 n>2 |
GL+(1,R) is isomorphic to R+ and is simply connected | M(n,R) | n2 | |
SL(n,R) | special linear group: real matrices with determinant 1 | N | 0 | Z n=2 Z2 n>2 |
SL(1,R) is a single point and therefore compact and simply connected | sl(n,R) | n2−1 | |
SL(2,R) | Orientation-preserving isometries of the Poincaré half-plane, isomorphic to SU(1,1), isomorphic to Sp(2,R). | N | 0 | Z | The universal cover has no finite-dimensional faithful representations. | sl(2,R) | 3 | |
O(n) | orthogonal group: real orthogonal matrices | Y | Z2 | – | The symmetry group of the sphere (n=3) or hypersphere. | so(n) | n(n−1)/2 | |
SO(n) | special orthogonal group: real orthogonal matrices with determinant 1 | Y | 0 | Z n=2 Z2 n>2 |
Spin(n) n>2 |
SO(1) is a single point and SO(2) is isomorphic to the circle group, SO(3) is the rotation group of the sphere. | so(n) | n(n−1)/2 |
Spin(n) | spin group: double cover of SO(n) | Y | 0 n>1 | 0 n>2 | Spin(1) is isomorphic to Z2 and not connected; Spin(2) is isomorphic to the circle group and not simply connected | so(n) | n(n−1)/2 | |
Sp(2n,R) | symplectic group: real symplectic matrices | N | 0 | Z | sp(2n,R) | n(2n+1) | ||
Sp(n) | compact symplectic group: quaternionic n×n unitary matrices | Y | 0 | 0 | sp(n) | n(2n+1) | ||
Mp(2n,R) | metaplectic group: double cover of real symplectic group Sp(2n,R) | Y | 0 | Z | Mp(2,R) is a Lie group that is not algebraic | sp(2n,R) | n(2n+1) | |
U(n) | unitary group: complex n×n unitary matrices | Y | 0 | Z | R×SU(n) | For n=1: isomorphic to S1. Note: this is not a complex Lie group/algebra | u(n) | n2 |
SU(n) | special unitary group: complex n×n unitary matrices with determinant 1 | Y | 0 | 0 | Note: this is not a complex Lie group/algebra | su(n) | n2−1 |
Lie algebra | Description | Simple? | Semi-simple? | Remarks | dim/R |
---|---|---|---|---|---|
R | the real numbers, the Lie bracket is zero | 1 | |||
Rn | the Lie bracket is zero | n | |||
R3 | the Lie bracket is the cross product | Yes | Yes | 3 | |
H | quaternions, with Lie bracket the commutator | 4 | |||
Im(H) | quaternions with zero real part, with Lie bracket the commutator; isomorphic to real 3-vectors,
with Lie bracket the cross product; also isomorphic to su(2) and to so(3,R) |
Yes | Yes | 3 | |
M(n,R) | n×n matrices, with Lie bracket the commutator | n2 | |||
sl(n,R) | square matrices with trace 0, with Lie bracket the commutator | Yes | Yes | n2−1 | |
so(n) | skew-symmetric square real matrices, with Lie bracket the commutator. | Yes, except n=4 | Yes | Exception: so(4) is semi-simple,
but not simple. |
n(n−1)/2 |
sp(2n,R) | real matrices that satisfy JA + ATJ = 0 where J is the standard skew-symmetric matrix | Yes | Yes | n(2n+1) | |
sp(n) | square quaternionic matrices A satisfying A = −A∗, with Lie bracket the commutator | Yes | Yes | n(2n+1) | |
u(n) | square complex matrices A satisfying A = −A∗, with Lie bracket the commutator | Note: this is not a complex Lie algebra | n2 | ||
su(n) n≥2 |
square complex matrices A with trace 0 satisfying A = −A∗, with Lie bracket the commutator | Yes | Yes | Note: this is not a complex Lie algebra | n2−1 |
Note that a "complex Lie group" is defined as a complex analytic manifold that is also a group whose multiplication and inversion are each given by a holomorphic map. The dimensions in the table below are dimensions over C. Note that every complex Lie group/algebra can also be viewed as a real Lie group/algebra of twice the dimension.
Lie group | Description | Cpt | UC | Remarks | Lie algebra | dim/C | ||
---|---|---|---|---|---|---|---|---|
Cn | group operation is addition | N | 0 | 0 | abelian | Cn | n | |
C× | nonzero complex numbers with multiplication | N | 0 | Z | abelian | C | 1 | |
GL(n,C) | general linear group: invertible n×n complex matrices | N | 0 | Z | For n=1: isomorphic to C× | M(n,C) | n2 | |
SL(n,C) | special linear group: complex matrices with determinant
1 |
N | 0 | 0 | for n=1 this is a single point and thus compact. | sl(n,C) | n2−1 | |
SL(2,C) | Special case of SL(n,C) for n=2 | N | 0 | 0 | Isomorphic to Spin(3,C), isomorphic to Sp(2,C) | sl(2,C) | 3 | |
PSL(2,C) | Projective special linear group | N | 0 | Z2 | SL(2,C) | Isomorphic to the Möbius group, isomorphic to the restricted Lorentz group SO+(3,1,R), isomorphic to SO(3,C). | sl(2,C) | 3 |
O(n,C) | orthogonal group: complex orthogonal matrices | N | Z2 | – | finite for n=1 | so(n,C) | n(n−1)/2 | |
SO(n,C) | special orthogonal group: complex orthogonal matrices with determinant 1 | N | 0 | Z n=2 Z2 n>2 |
SO(2,C) is abelian and isomorphic to C×; nonabelian for n>2. SO(1,C) is a single point and thus compact and simply connected | so(n,C) | n(n−1)/2 | |
Sp(2n,C) | symplectic group: complex symplectic matrices | N | 0 | 0 | sp(2n,C) | n(2n+1) |
The dimensions given are dimensions over C. Note that every complex Lie algebra can also be viewed as a real Lie algebra of twice the dimension.
Lie algebra | Description | Simple? | Semi-simple? | Remarks | dim/C |
---|---|---|---|---|---|
C | the complex numbers | 1 | |||
Cn | the Lie bracket is zero | n | |||
M(n,C) | n×n matrices with Lie bracket the commutator | n2 | |||
sl(n,C) | square matrices with trace 0 with Lie bracket
the commutator |
Yes | Yes | n2−1 | |
sl(2,C) | Special case of sl(n,C) with n=2 | Yes | Yes | isomorphic to su(2) |
3 |
so(n,C) | skew-symmetric square complex matrices with Lie bracket
the commutator |
Yes, except n=4 | Yes | Exception: so(4,C) is semi-simple,
but not simple. |
n(n−1)/2 |
sp(2n,C) | complex matrices that satisfy JA + ATJ = 0
where J is the standard skew-symmetric matrix |
Yes | Yes | n(2n+1) |
The Lie algebra of affine transformations of dimension two, in fact, exist for any field. An instance has already been listed in the first table for real Lie algebras.
![]() | Original source: https://en.wikipedia.org/wiki/Table of Lie groups.
Read more |