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8-orthoplex	Rectified 8-orthoplex	Birectified 8-orthoplex	Trirectified 8-orthoplex
Trirectified 8-cube	Birectified 8-cube	Rectified 8-cube	8-cube
Orthogonal projections in A8 Coxeter plane

In eight-dimensional geometry, a rectified 8-orthoplex is a convex uniform 8-polytope, being a rectification of the regular 8-orthoplex.

There are unique 8 degrees of rectifications, the zeroth being the 8-orthoplex, and the 7th and last being the 8-cube. Vertices of the rectified 8-orthoplex are located at the edge-centers of the 8-orthoplex. Vertices of the birectified 8-orthoplex are located in the triangular face centers of the 8-orthoplex. Vertices of the trirectified 8-orthoplex are located in the tetrahedral cell centers of the 8-orthoplex.

Rectified 8-orthoplex

Rectified 8-orthoplex
Type	uniform 8-polytope
Schläfli symbol	t1{3,3,3,3,3,3,4}
Coxeter-Dynkin diagrams
7-faces	272
6-faces	3072
5-faces	8960
4-faces	12544
Cells	10080
Faces	4928
Edges	1344
Vertices	112
Vertex figure	6-orthoplex prism
Petrie polygon	hexakaidecagon
Coxeter groups	C8, D8,
Properties	convex

The rectified 8-orthoplex has 112 vertices. These represent the root vectors of the simple Lie group D₈. The vertices can be seen in 3 hyperplanes, with the 28 vertices rectified 7-simplexs cells on opposite sides, and 56 vertices of an expanded 7-simplex passing through the center. When combined with the 16 vertices of the 8-orthoplex, these vertices represent the 128 root vectors of the B₈ and C₈ simple Lie groups.

Related polytopes

The rectified 8-orthoplex is the vertex figure for the demiocteractic honeycomb.

or

Alternate names

• rectified octacross
• rectified diacosipentacontahexazetton (Acronym: rek) (Jonathan Bowers)

Construction

There are two Coxeter groups associated with the rectified 8-orthoplex, one with the C₈ or Coxeter group, and a lower symmetry with two copies of heptcross facets, alternating, with the D₈ or Coxeter group.

Cartesian coordinates

Cartesian coordinates for the vertices of a rectified 8-orthoplex, centered at the origin, edge length ${\displaystyle {\sqrt {2}}}$ are all permutations of:

(±1,±1,0,0,0,0,0,0)

Images

orthographic projections

B8			B7
B6			B5
B4		B3		B2
A7		A5		A3

Birectified 8-orthoplex

Birectified 8-orthoplex
Type	uniform 8-polytope
Schläfli symbol	t2{3,3,3,3,3,3,4}
Coxeter-Dynkin diagrams
7-faces	272
6-faces	3184
5-faces	16128
4-faces	34048
Cells	36960
Faces	22400
Edges	6720
Vertices	448
Vertex figure	{3,3,3,4}x{3}
Coxeter groups	C8, D8,
Properties	convex

Alternate names

• birectified octacross
• birectified diacosipentacontahexazetton (Acronym: bark) (Jonathan Bowers)

Cartesian coordinates

Cartesian coordinates for the vertices of a birectified 8-orthoplex, centered at the origin, edge length ${\displaystyle {\sqrt {2}}}$ are all permutations of:

(±1,±1,±1,0,0,0,0,0)

Images

orthographic projections

B8			B7
B6			B5
B4		B3		B2
A7		A5		A3

Trirectified 8-orthoplex

Trirectified 8-orthoplex
Type	uniform 8-polytope
Schläfli symbol	t3{3,3,3,3,3,3,4}
Coxeter-Dynkin diagrams
7-faces	16+256
6-faces	1024 + 2048 + 112
5-faces	1792 + 7168 + 7168 + 448
4-faces	1792 + 10752 + 21504 + 14336
Cells	8960 + 126880 + 35840
Faces	17920 + 35840
Edges	17920
Vertices	1120
Vertex figure	{3,3,4}x{3,3}
Coxeter groups	C8, D8,
Properties	convex

The trirectified 8-orthoplex can tessellate space in the quadrirectified 8-cubic honeycomb.

Alternate names

• trirectified octacross
• trirectified diacosipentacontahexazetton (acronym: tark) (Jonathan Bowers)

Cartesian coordinates

Cartesian coordinates for the vertices of a trirectified 8-orthoplex, centered at the origin, edge length ${\displaystyle {\sqrt {2}}}$ are all permutations of:

(±1,±1,±1,±1,0,0,0,0)

Images

orthographic projections

B8			B7
B6			B5
B4		B3		B2
A7		A5		A3

Notes

1. Klitzing, (o3x3o3o3o3o3o4o - rek)
2. Klitzing, (o3o3x3o3o3o3o4o - bark)
3. Klitzing, (o3o3o3x3o3o3o4o - tark)

References

• H.S.M. Coxeter:
  • H.S.M. Coxeter, Regular Polytopes, 3rd Edition, Dover New York, 1973
  • 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
    • (Paper 22) H.S.M. Coxeter, Regular and Semi Regular Polytopes I,
    • (Paper 23) H.S.M. Coxeter, Regular and Semi-Regular Polytopes II,
    • (Paper 24) H.S.M. Coxeter, Regular and Semi-Regular Polytopes III,
• Norman Johnson Uniform Polytopes, Manuscript (1991)
  • N.W. Johnson: The Theory of Uniform Polytopes and Honeycombs, Ph.D.
• Klitzing, Richard. "8D uniform polytopes (polyzetta)". o3x3o3o3o3o3o4o - rek, o3o3x3o3o3o3o4o - bark, o3o3o3x3o3o3o4o - tark

External links

• Polytopes of Various Dimensions
• Multi-dimensional Glossary

• 8-polytopes