List of finite spherical symmetry groups

Short description: None

Finite spherical symmetry groups are also called point groups in three dimensions. There are five fundamental symmetry classes which have triangular fundamental domains: dihedral, cyclic, tetrahedral, octahedral, and icosahedral symmetry.

This article lists the groups by Schoenflies notation, Coxeter notation,[1] orbifold notation,[2] and order. John Conway uses a variation of the Schoenflies notation, based on the groups' quaternion algebraic structure, labeled by one or two upper case letters, and whole number subscripts. The group order is defined as the subscript, unless the order is doubled for symbols with a plus or minus, "±", prefix, which implies a central inversion.[3]

Hermann–Mauguin notation (International notation) is also given. The crystallography groups, 32 in total, are a subset with element orders 2, 3, 4 and 6.[4]

## Contents

* 1 Involutional symmetry
* 2 Cyclic symmetry
* 3 Dihedral symmetry
* 4 Polyhedral symmetry
* 5 Continuous symmetries
* 6 See also
* 7 References
* 8 Further reading
* 9 External links

## Involutional symmetry

There are four involutional groups: no symmetry (C1), reflection symmetry (Cs), 2-fold rotational symmetry (C2), and central point symmetry (Ci).

Intl | Geo
| Orbifold | Schönflies  | Conway | Coxeter  | Order  | Abstract | Fund.
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1  | 1 | 11  | C1 | C1 | ][
[ ]+ |  | 1  | Z1 |
2  | 2 | 22  | D1
= C2 | D2
= C2 | [2]+ |  | 2  | Z2 |
1 | 22 | ×  | Ci
= S2 | CC2 | [2+,2+] |  | 2  | Z2 |

= m  | 1  | *  | Cs
= C1v
= C1h | ±C1
= CD2 | [ ] |  | 2  | Z2 |

## Cyclic symmetry

There are four infinite cyclic symmetry families, with n = 2 or higher. (n may be 1 as a special case as no symmetry)

Intl | Geo
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4 | 42 | 2×  | S4 | CC4 | [2+,4+] |  | 4  | Z4 |
2/m  | 22  | 2*  | C2h
= D1d | ±C2
= ±D2 | [2,2+]
[2+,2] |
| 4  | Z4 |
Intl | Geo
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n  | 2

n | 22

nn  | C2

Cn | C2

Cn | [2]+
[3]+
[4]+
[5]+
[6]+
[n]+ |

| 2

n  | Z2

Zn |
2mm

4mm

6mm
nm (n is odd)
nmm (n is even)  | 2

n  | *22
*33
*44
*55
*66
*nn  | C2v
C3v
C4v
C5v
C6v
Cnv | CD4
CD6
CD8
CD10
CD12
CD2n | [2]
[3]
[4]
[5]
[6]
[n] |

| 4

2n  | D4

D10
D12
D2n |

\-  | 62

10.2
12.2
2n.2 | 3×

n×  | S6

S10
S12
S2n | ±C3
CC8
±C5
CC12
CC2n / ±Cn | [2+,6+]
[2+,8+]
[2+,10+]
[2+,12+]
[2+,2n+] |

| 6

2n  | Z6

Z10
Z12
Z2n |
3/m=6
4/m
5/m=10
6/m
n/m  | 32

n2  | 3*

n*  | C3h
C4h
C5h
C6h
Cnh | CC6
±C4
CC10
±C6
±Cn / CC2n | [2,3+]
[2,4+]
[2,5+]
[2,6+]
[2,n+] |

| 6

2n  | Z6
Z2×Z4
Z10
Z2×Z6
Z2×Zn
≅Z2n (odd n)  |

## Dihedral symmetry

There are three infinite dihedral symmetry families, with n = 2 or higher (n may be 1 as a special case).

Intl | Geo
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222  | 2.2 | 222  | D2 | D4 | [2,2]+
| 4  | D4 |
42m  | 42 | 2*2  | D2d | DD8 | [2+,4]
| 8  | D4 |
mmm  | 22  | *222  | D2h | ±D4 | [2,2]
| 8  | Z2×D4 |
Intl | Geo
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422

622  | 3.2
4.2
5.2
6.2
n.2 | 223
224
225
226
22n  | D3

Dn | D6

D10
D12
D2n | [2,3]+
[2,4]+
[2,5]+
[2,6]+
[2,n]+ |

| 6

2n | D6

D10
D12
D2n |

82m

12.2m
| 62

10.2
12.2

| 2*3
2*4
2*5
2*6
2*n  | D3d
D4d
D5d
D6d
Dnd | ±D6
DD16
±D10
DD24
DD4n / ±D2n | [2+,6]
[2+,8]
[2+,10]
[2+,12]
[2+,2n] |

| 12

4n  | D12
D16
D20
D24
D4n |
6m2
4/mmm
10m2
6/mmm  | 32

n2  | *223
*224
*225
*226
*22n  | D3h
D4h
D5h
D6h
Dnh | DD12
±D8
DD20
±D12
±D2n / DD4n | [2,3]
[2,4]
[2,5]
[2,6]
[2,n] |

| 12

4n  | D12
Z2×D8
D20
Z2×D12
Z2×D2n
≅D4n (odd n)  |

## Polyhedral symmetry

Further information: Polyhedral groups

There are three types of polyhedral symmetry: tetrahedral symmetry, octahedral symmetry, and icosahedral symmetry, named after the triangle-faced regular polyhedra with these symmetries.

Tetrahedral symmetry Intl | Geo
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23  | 3.3 | 332  | T  | T  | [3,3]+
| 12  | A4 |
m3 | 43 | 3*2  | Th | ±T  | [4,3+]
| 24  | 2×A4 |
43m  | 33  | *332  | Td | TO  | [3,3]
| 24  | S4 |
Octahedral symmetry Intl | Geo
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432  | 4.3 | 432  | O  | O  | [4,3]+
| 24  | S4 |
m3m  | 43  | *432  | Oh | ±O  | [4,3]
| 48  | 2×S4 |
Icosahedral symmetry Intl | Geo
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532  | 5.3 | 532  | I  | I  | [5,3]+
| 60  | A5 |
532/m  | 53  | *532  | Ih | ±I  | [5,3]
| 120  | 2×A5 |

## Continuous symmetries

All of the discrete point symmetries are subgroups of certain continuous symmetries. They can be classified as products of orthogonal groups O(n) or special orthogonal groups SO(n). O(1) is a single orthogonal reflection, dihedral symmetry order 2, Dih1. SO(1) is just the identity. Half turns, C2, are needed to complete.

Rank 3 groups | Other names | Example geometry | Example finite subgroups

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O(3) |  | Full symmetry of the sphere |  | [3,3] = , [4,3] = , [5,3] =
[4,3+] =
SO(3) | Sphere group | Rotational symmetry | [3,3]+ = , [4,3]+ = , [5,3]+ =
O(2)×O(1)
O(2)⋊C2 | Dih∞×Dih1
Dih∞⋊C2 | Full symmetry of a spheroid, torus, cylinder, bicone or hyperboloid
Full circular symmetry with half turn | 100px45px48px | [p,2] = [p]×[ ] =
[2p,2+] = , [2p+,2+] =
SO(2)×O(1) | C∞×Dih1 | Rotational symmetry with reflection | [p+,2] = [p]+×[ ] =
SO(2)⋊C2 | C∞⋊C2 | Rotational symmetry with half turn | [p,2]+ =
O(2)×SO(1) | Dih∞
Circular symmetry | Full symmetry of a hemisphere, cone, paraboloid
or any surface of revolution | 85px70px | [p,1] = [p] =
SO(2)×SO(1) | C∞
Circle group | Rotational symmetry | [p,1]+ = [p]+ =

## See also

* Crystallographic point group
* Triangle group
* List of planar symmetry groups
* Point groups in two dimensions

## References

1. ↑ Johnson, 2015
2. ↑ Conway, John H. (2008). The symmetries of things. Wellesley, Mass: A.K. Peters. ISBN 978-1-56881-220-5. OCLC 181862605.
3. ↑ Conway, John; Smith, Derek A. (2003). On quaternions and octonions: their geometry, arithmetic, and symmetry. Natick, Mass: A.K. Peters. ISBN 978-1-56881-134-5. OCLC 560284450.
4. ↑ Sands, 1993

## Further reading

* Peter R. Cromwell, Polyhedra (1997), Appendix I
* Sands, Donald E. (1993). "Crystal Systems and Geometry". Introduction to Crystallography. Mineola, New York: Dover Publications, Inc.. p. 165. ISBN 0-486-67839-3.
* On Quaternions and Octonions, 2003, John Horton Conway and Derek A. Smith ISBN 978-1-56881-134-5
* The Symmetries of Things 2008, John H. Conway, Heidi Burgiel, Chaim Goodman-Strauss, ISBN 978-1-56881-220-5
* Kaleidoscopes: Selected Writings of H.S.M. Coxeter, edited by F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss, Wiley-Interscience Publication, 1995, ISBN 978-0-471-01003-6 [1]
* (Paper 22) H.S.M. Coxeter, Regular and Semi Regular Polytopes I, [Math. Zeit. 46 (1940) 380–407, MR 2,10]
* (Paper 23) H.S.M. Coxeter, Regular and Semi-Regular Polytopes II, [Math. Zeit. 188 (1985) 559–591]
* (Paper 24) H.S.M. Coxeter, Regular and Semi-Regular Polytopes III, [Math. Zeit. 200 (1988) 3–45]
* N.W. Johnson: Geometries and Transformations, (2018) ISBN 978-1-107-10340-5 Chapter 11: Finite symmetry groups, Table 11.4 Finite Groups of Isometries in 3-space

## External links

* Finite spherical symmetry groups
* Weisstein, Eric W.. "Schoenflies symbol". http://mathworld.wolfram.com/SchoenfliesSymbol.html.
* Weisstein, Eric W.. "Crystallographic point groups". http://mathworld.wolfram.com/CrystallographicPointGroups.html.
* Simplest Canonical Polyhedra of Each Symmetry Type, by David I. McCooey

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