Dihedral Group D_4
The dihedral group 👁 D_4
is one of the two non-Abelian groups of the five groups
total of group order 8. It is sometimes called the
octic group. An example of 👁 D_4
is the symmetry group of the square.
The cycle graph of 👁 D_4
is shown above. 👁 D_4
has cycle index given by
Its multiplication table is illustrated above.
👁 D_4
has representation
| 👁 I | 👁 = | 👁 [1 0; 0 1] |
(2)
|
| 👁 A | 👁 = | 👁 [0 -1; 1 0] |
(3)
|
| 👁 B | 👁 = | 👁 [-1 0; 0 -1] |
(4)
|
| 👁 C | 👁 = | 👁 [0 1; -1 0] |
(5)
|
| 👁 D | 👁 = | 👁 [-1 0; 0 1] |
(6)
|
| 👁 E | 👁 = | 👁 [0 1; 1 0] |
(7)
|
| 👁 F | 👁 = | 👁 [1 0; 0 -1] |
(8)
|
| 👁 G | 👁 = | 👁 [0 -1; -1 0]. |
(9)
|
Conjugacy classes include 👁 {I}
, 👁 {B}
, 👁 {A,C}
, 👁 {D,F}
, and 👁 {E,G}
. There are 10 subgroups of 👁 D_4
: 👁 {I}
, 👁 {I,B}
, 👁 {I,D}
, 👁 {I,E}
, 👁 {I,F}
, 👁 {I,G}
, 👁 {I,A,B,C}
, 👁 {I,B,D,F}
, and 👁 {I,B,E,G}
, 👁 {1,A,B,C,D,E,F,G}
. Of these, 👁 {1}
, 👁 {1,B}
, 👁 {1,A,B,C}
, 👁 {1,B,D,F}
, 👁 {1,B,E,G}
, and 👁 {1,A,B,C,D,E,F,G}
are normal
See also
Cyclic Group C8, Dihedral Group, Dihedral Group D3, Dihedral Group D5, Finite Group C2×C2×C2, Finite Group C2×C4Explore with Wolfram|Alpha
More things to try:
References
Cotton, F. A. Chemical Applications of Group Theory, 3rd ed. New York: Wiley, 1990.Referenced on Wolfram|Alpha
Dihedral Group D_4Cite this as:
Weisstein, Eric W. "Dihedral Group D_4." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/DihedralGroupD4.html
