Special unitary group
The simply connected compact group with Lie algebra su(2). Its irreducible complex representations are indexed by spin j = 0, ½, 1, … .
Reference properties
Representations
Highest weight n = 2j ≥ 0; dimension n + 1. Even n has real type, odd n quaternionic type. [sources]
Topology and global form
SU(2) is diffeomorphic to S³. The central quotient by {±I} is SO(3). [sources]
In physics
Angular momentum, spin, weak isospin, and the basic example of a spin cover. [sources]
Names and aliases
Spin(3) · Sp(1)
Related objects and maps
- Related group
- Related group
- Related group
- Actual real Lie algebra
- Real-form context
- Explicit homomorphism
- Explicit homomorphism
- Explicit homomorphism
- Explicit homomorphism
- Specified homogeneous quotient
Claims and sources
Each assertion has a stable identifier within this record and a source locator or derivation. Cite the dataset edition when referring to a corrected or historical claim.
Definition
2 × 2 complex unitary matrices of determinant 1
- Lie Groups and Lie AlgebrasSections 6.1–6.3: classical matrix groups and their Lie algebrasOpen source
group:su-2#definitionReal dimension
3
- Lie Groups and Lie AlgebrasSections 6.1–6.3: su(2) consists of traceless skew-Hermitian 2 × 2 matrices; real dimension 2²−1=3Open source
group:su-2#dimensionCenter
ℤ₂
- Math 210C. Centers of simply connected semisimple groupsPages 1–2: type A₁ and SU(2) center μ₂Open source
group:su-2#centerFundamental group
0
- Lie Groups and Lie AlgebrasSection 4.17, printed page 31: SU(2)/U(1) and SO(3)/SO(2) as S²; SU(2)=S³ and SO(3)=RP³Open source
- Conrad and Landesman · Compact Lie groupsLecture 16, including (16.6), and Appendix P: Spin(n) as the simply connected double cover for n ≥ 3Open source
group:su-2#pi1Compact
Yes
- Lie Groups and Lie AlgebrasSections 6.1–6.3: classical matrix groups and their Lie algebrasOpen source
group:su-2#compactConnected
Yes
- Conrad and Landesman · Compact Lie groupsLectures 26–28 and Appendix V: compact semisimple groups and highest weightsOpen source
- Conrad and Landesman · Compact Lie groupsLecture 16, printed page 73: SU(n) and Sp(n) are simply connectedOpen source
group:su-2#connectedRank
1
- Conrad and Landesman · Compact Lie groupsLecture 25 and Appendix T: root systems and classical root computationsOpen source
group:su-2#rankRepresentations
Highest weight n = 2j ≥ 0; dimension n + 1. Even n has real type, odd n quaternionic type.
- Lie Groups and Lie AlgebrasSection 11.4: irreducible sl(2,C) modules of highest weight n and dimension n+1Open source
- Lecture 6: Maximal Root, Exponents, Coxeter Numbers, Dual RepresentationsSection 32.5, Example 32.13, printed page 176: even n has real type and odd n has quaternionic typeOpen source
group:su-2#representations-1Topology and global form
SU(2) is diffeomorphic to S³. The central quotient by {±I} is SO(3).
- Lie Groups and Lie AlgebrasSection 4.17, printed page 31: SU(2)/U(1) and SO(3)/SO(2) as S²; SU(2)=S³ and SO(3)=RP³Open source
group:su-2#topology-1In physics
Angular momentum, spin, weak isospin, and the basic example of a spin cover.
- Lie Groups and Lie AlgebrasSection 11.4: irreducible sl(2,C) modules of highest weight n and dimension n+1Open source
- Lecture 6: Maximal Root, Exponents, Coxeter Numbers, Dual RepresentationsSection 32.5, Example 32.13, printed page 176: even n has real type and odd n has quaternionic typeOpen source
group:su-2#physics-1Related group
group:so-3
- Lie Groups and Lie AlgebrasSections 6.1–6.3: classical matrix groups and their Lie algebrasOpen source
group:su-2#relation-1Related group
group:q-8
- Lie Groups and Lie AlgebrasSections 6.1–6.3: classical matrix groups and their Lie algebrasOpen source
group:su-2#relation-2Related group
group:su-3
- Lie Groups and Lie AlgebrasSections 6.1–6.3: classical matrix groups and their Lie algebrasOpen source
group:su-2#relation-3Actual real Lie algebra
algebra:su-2-r
- Lie Groups and Lie AlgebrasSections 6.1–6.3: classical matrix groups and their Lie algebrasOpen source
- Lecture 15: Classification of Real Forms of Semisimple Lie AlgebrasSections 41.2–41.4: compact, split, and classical real formsOpen source
group:su-2#relation-4Real-form context
real-form:su-2-r
- Lecture 15: Classification of Real Forms of Semisimple Lie AlgebrasSections 41.2–41.4: compact, split, and classical real formsOpen source
group:su-2#relation-5Explicit homomorphism
map:su-2-to-so-3
- Sporadic isogenies to orthogonal groupsSection 2.1: SU(2) → SO(3), construction and kernelOpen source
group:su-2#relation-6Explicit homomorphism
map:su-2-to-su-3-regular
- Haber · Spin covers and subgroup examplesProblem 5, pages 14–15: block SU(2) subgroup of SU(3)Open source
group:su-2#relation-7Explicit homomorphism
map:su-2-to-su-3-principal
- Haber · Spin covers and subgroup examplesProblem 5, pages 14–15: the irreducible three-dimensional SU(2) action and SO(3) imageOpen source
group:su-2#relation-8Explicit homomorphism
map:u-1-to-su-2
- Lie Groups and Lie AlgebrasSections 6.1–6.3: classical matrix groups and their Lie algebrasOpen source
- Lie Groups and Lie AlgebrasSection 4.17, printed page 31: SU(2)/U(1) and SO(3)/SO(2) as S²; SU(2)=S³ and SO(3)=RP³Open source
group:su-2#relation-9Specified homogeneous quotient
space:su-2-over-u-1
- Lie Groups and Lie AlgebrasSection 4.17, printed page 31: SU(2)/U(1) and SO(3)/SO(2) as S²; SU(2)=S³ and SO(3)=RP³Open source
group:su-2#relation-10