6-simplex
Type uniform polypeton
Schläfli symbol {35}
Coxeter diagrams
Elements

f5 = 7, f4 = 21, C = 35, F = 35, E = 21, V = 7
(χ=0)

Coxeter group A6, [35], order 5040
Bowers name
and (acronym)
Heptapeton
(hop)
Vertex figure 5-simplex
Circumradius ${\displaystyle {\sqrt {\tfrac {3}{7))))$
0.654654[1]
Properties convex, isogonal self-dual

In geometry, a 6-simplex is a self-dual regular 6-polytope. It has 7 vertices, 21 edges, 35 triangle faces, 35 tetrahedral cells, 21 5-cell 4-faces, and 7 5-simplex 5-faces. Its dihedral angle is cos−1(1/6), or approximately 80.41°.

## Alternate names

It can also be called a heptapeton, or hepta-6-tope, as a 7-facetted polytope in 6-dimensions. The name heptapeton is derived from hepta for seven facets in Greek and -peta for having five-dimensional facets, and -on. Jonathan Bowers gives a heptapeton the acronym hop.[2]

## As a configuration

This configuration matrix represents the 6-simplex. The rows and columns correspond to vertices, edges, faces, cells, 4-faces and 5-faces. The diagonal numbers say how many of each element occur in the whole 6-simplex. The nondiagonal numbers say how many of the column's element occur in or at the row's element. This self-dual simplex's matrix is identical to its 180 degree rotation.[3][4]

${\displaystyle {\begin{bmatrix}{\begin{matrix}7&6&15&20&15&6\\2&21&5&10&10&5\\3&3&35&4&6&4\\4&6&4&35&3&3\\5&10&10&5&21&2\\6&15&20&15&6&7\end{matrix))\end{bmatrix))}$

## Coordinates

The Cartesian coordinates for an origin-centered regular heptapeton having edge length 2 are:

${\displaystyle \left({\sqrt {1/21)),\ {\sqrt {1/15)),\ {\sqrt {1/10)),\ {\sqrt {1/6)),\ {\sqrt {1/3)),\ \pm 1\right)}$
${\displaystyle \left({\sqrt {1/21)),\ {\sqrt {1/15)),\ {\sqrt {1/10)),\ {\sqrt {1/6)),\ -2{\sqrt {1/3)),\ 0\right)}$
${\displaystyle \left({\sqrt {1/21)),\ {\sqrt {1/15)),\ {\sqrt {1/10)),\ -{\sqrt {3/2)),\ 0,\ 0\right)}$
${\displaystyle \left({\sqrt {1/21)),\ {\sqrt {1/15)),\ -2{\sqrt {2/5)),\ 0,\ 0,\ 0\right)}$
${\displaystyle \left({\sqrt {1/21)),\ -{\sqrt {5/3)),\ 0,\ 0,\ 0,\ 0\right)}$
${\displaystyle \left(-{\sqrt {12/7)),\ 0,\ 0,\ 0,\ 0,\ 0\right)}$

The vertices of the 6-simplex can be more simply positioned in 7-space as permutations of:

(0,0,0,0,0,0,1)

This construction is based on facets of the 7-orthoplex.

## Images

orthographic projections
Ak Coxeter plane A6 A5 A4
Graph
Dihedral symmetry [7] [6] [5]
Ak Coxeter plane A3 A2
Graph
Dihedral symmetry [4] [3]

## Related uniform 6-polytopes

The regular 6-simplex is one of 35 uniform 6-polytopes based on the [3,3,3,3,3] Coxeter group, all shown here in A6 Coxeter plane orthographic projections.

A6 polytopes

t0

t1

t2

t0,1

t0,2

t1,2

t0,3

t1,3

t2,3

t0,4

t1,4

t0,5

t0,1,2

t0,1,3

t0,2,3

t1,2,3

t0,1,4

t0,2,4

t1,2,4

t0,3,4

t0,1,5

t0,2,5

t0,1,2,3

t0,1,2,4

t0,1,3,4

t0,2,3,4

t1,2,3,4

t0,1,2,5

t0,1,3,5

t0,2,3,5

t0,1,4,5

t0,1,2,3,4

t0,1,2,3,5

t0,1,2,4,5

t0,1,2,3,4,5

## Notes

1. ^ Klitzing, Richard. "heptapeton". bendwavy.org.
2. ^ Klitzing, Richard. "6D uniform polytopes (polypeta) x3o3o3o3o3o — hop".
3. ^ Coxeter 1973, §1.8 Configurations
4. ^ Coxeter, H.S.M. (1991). Regular Complex Polytopes (2nd ed.). Cambridge University Press. p. 117. ISBN 9780521394901.

## References

Family An Bn I2(p) / Dn E6 / E7 / E8 / F4 / G2 Hn
Regular polygon Triangle Square p-gon Hexagon Pentagon
Uniform polyhedron Tetrahedron OctahedronCube Demicube DodecahedronIcosahedron
Uniform polychoron Pentachoron 16-cellTesseract Demitesseract 24-cell 120-cell600-cell
Uniform 5-polytope 5-simplex 5-orthoplex5-cube 5-demicube
Uniform 6-polytope 6-simplex 6-orthoplex6-cube 6-demicube 122221
Uniform 7-polytope 7-simplex 7-orthoplex7-cube 7-demicube 132231321
Uniform 8-polytope 8-simplex 8-orthoplex8-cube 8-demicube 142241421
Uniform 9-polytope 9-simplex 9-orthoplex9-cube 9-demicube
Uniform 10-polytope 10-simplex 10-orthoplex10-cube 10-demicube
Uniform n-polytope n-simplex n-orthoplexn-cube n-demicube 1k22k1k21 n-pentagonal polytope
Topics: Polytope familiesRegular polytopeList of regular polytopes and compounds