- Source: 8-simplex
- Daftar bentuk matematika
- Crux simplex
- TORCH
- Asiklovir
- Grup titik
- Anisakiasis
- Metode Nelder-Mead
- Ngancar, Kediri
- Coventry Climax
- Merbah
- 8-simplex
- Simplex
- 8-simplex honeycomb
- Cyclotruncated 8-simplex honeycomb
- Stericated 8-simplexes
- Runcinated 8-simplexes
- Herpes simplex virus
- Herpes
- List of mathematical shapes
- List of polygons, polyhedra and polytopes
In geometry, an 8-simplex is a self-dual regular 8-polytope. It has 9 vertices, 36 edges, 84 triangle faces, 126 tetrahedral cells, 126 5-cell 4-faces, 84 5-simplex 5-faces, 36 6-simplex 6-faces, and 9 7-simplex 7-faces. Its dihedral angle is cos−1(1/8), or approximately 82.82°.
It can also be called an enneazetton, or ennea-8-tope, as a 9-facetted polytope in eight-dimensions. The name enneazetton is derived from ennea for nine facets in Greek and -zetta for having seven-dimensional facets, and -on.
As a configuration
This configuration matrix represents the 8-simplex. The rows and columns correspond to vertices, edges, faces, cells, 4-faces, 5-faces, 6-faces and 7-faces. The diagonal numbers say how many of each element occur in the whole 8-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.
[
9
8
28
56
70
56
28
8
2
36
7
21
35
35
21
7
3
3
84
6
15
20
15
6
4
6
4
126
5
10
10
5
5
10
10
5
126
4
6
4
6
15
20
15
6
84
3
3
7
21
35
35
21
7
36
2
8
28
56
70
56
28
8
9
]
{\displaystyle {\begin{bmatrix}{\begin{matrix}9&8&28&56&70&56&28&8\\2&36&7&21&35&35&21&7\\3&3&84&6&15&20&15&6\\4&6&4&126&5&10&10&5\\5&10&10&5&126&4&6&4\\6&15&20&15&6&84&3&3\\7&21&35&35&21&7&36&2\\8&28&56&70&56&28&8&9\end{matrix}}\end{bmatrix}}}
Coordinates
The Cartesian coordinates of the vertices of an origin-centered regular enneazetton having edge length 2 are:
(
1
/
6
,
1
/
28
,
1
/
21
,
1
/
15
,
1
/
10
,
1
/
6
,
1
/
3
,
±
1
)
{\displaystyle \left(1/6,\ {\sqrt {1/28}},\ {\sqrt {1/21}},\ {\sqrt {1/15}},\ {\sqrt {1/10}},\ {\sqrt {1/6}},\ {\sqrt {1/3}},\ \pm 1\right)}
(
1
/
6
,
1
/
28
,
1
/
21
,
1
/
15
,
1
/
10
,
1
/
6
,
−
2
1
/
3
,
0
)
{\displaystyle \left(1/6,\ {\sqrt {1/28}},\ {\sqrt {1/21}},\ {\sqrt {1/15}},\ {\sqrt {1/10}},\ {\sqrt {1/6}},\ -2{\sqrt {1/3}},\ 0\right)}
(
1
/
6
,
1
/
28
,
1
/
21
,
1
/
15
,
1
/
10
,
−
3
/
2
,
0
,
0
)
{\displaystyle \left(1/6,\ {\sqrt {1/28}},\ {\sqrt {1/21}},\ {\sqrt {1/15}},\ {\sqrt {1/10}},\ -{\sqrt {3/2}},\ 0,\ 0\right)}
(
1
/
6
,
1
/
28
,
1
/
21
,
1
/
15
,
−
2
2
/
5
,
0
,
0
,
0
)
{\displaystyle \left(1/6,\ {\sqrt {1/28}},\ {\sqrt {1/21}},\ {\sqrt {1/15}},\ -2{\sqrt {2/5}},\ 0,\ 0,\ 0\right)}
(
1
/
6
,
1
/
28
,
1
/
21
,
−
5
/
3
,
0
,
0
,
0
,
0
)
{\displaystyle \left(1/6,\ {\sqrt {1/28}},\ {\sqrt {1/21}},\ -{\sqrt {5/3}},\ 0,\ 0,\ 0,\ 0\right)}
(
1
/
6
,
1
/
28
,
−
12
/
7
,
0
,
0
,
0
,
0
,
0
)
{\displaystyle \left(1/6,\ {\sqrt {1/28}},\ -{\sqrt {12/7}},\ 0,\ 0,\ 0,\ 0,\ 0\right)}
(
1
/
6
,
−
7
/
4
,
0
,
0
,
0
,
0
,
0
,
0
)
{\displaystyle \left(1/6,\ -{\sqrt {7/4}},\ 0,\ 0,\ 0,\ 0,\ 0,\ 0\right)}
(
−
4
/
3
,
0
,
0
,
0
,
0
,
0
,
0
,
0
)
{\displaystyle \left(-4/3,\ 0,\ 0,\ 0,\ 0,\ 0,\ 0,\ 0\right)}
More simply, the vertices of the 8-simplex can be positioned in 9-space as permutations of (0,0,0,0,0,0,0,0,1). This construction is based on facets of the 9-orthoplex.
Another origin-centered construction uses (1,1,1,1,1,1,1,1)/3 and permutations of (1,1,1,1,1,1,1,-11)/12 for edge length √2.
Images
Related polytopes and honeycombs
This polytope is a facet in the uniform tessellations: 251, and 521 with respective Coxeter-Dynkin diagrams:
,
This polytope is one of 135 uniform 8-polytopes with A8 symmetry.
References
Coxeter, H.S.M.:
— (1973). "Table I (iii): Regular Polytopes, three regular polytopes in n-dimensions (n≥5)". Regular Polytopes (3rd ed.). Dover. pp. 296. ISBN 0-486-61480-8.
Sherk, F. Arthur; McMullen, Peter; Thompson, Anthony C.; Weiss, Asia Ivic, eds. (1995). Kaleidoscopes: Selected Writings of H.S.M. Coxeter. Wiley. ISBN 978-0-471-01003-6.
(Paper 22) — (1940). "Regular and Semi Regular Polytopes I". Math. Zeit. 46: 380–407. doi:10.1007/BF01181449. S2CID 186237114.
(Paper 23) — (1985). "Regular and Semi-Regular Polytopes II". Math. Zeit. 188 (4): 559–591. doi:10.1007/BF01161657. S2CID 120429557.
(Paper 24) — (1988). "Regular and Semi-Regular Polytopes III". Math. Zeit. 200: 3–45. doi:10.1007/BF01161745. S2CID 186237142.
Conway, John H.; Burgiel, Heidi; Goodman-Strauss, Chaim (2008). "26. Hemicubes: 1n1". The Symmetries of Things. p. 409. ISBN 978-1-56881-220-5.
Johnson, Norman (1991). "Uniform Polytopes" (Manuscript). Norman Johnson (mathematician).
Johnson, N.W. (1966). The Theory of Uniform Polytopes and Honeycombs (PhD). University of Toronto. OCLC 258527038.
Klitzing, Richard. "8D uniform polytopes (polyzetta) x3o3o3o3o3o3o3o — ene".
External links
Glossary for hyperspace, George Olshevsky.
Polytopes of Various Dimensions
Multi-dimensional Glossary