Rectified 8-orthoplexes

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, [4,3^6] D8, [3^5,1,1]
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)^[1]

Construction

There are two Coxeter groups associated with the rectified 8-orthoplex, one with the C₈ or [4,3⁶] Coxeter group, and a lower symmetry with two copies of heptcross facets, alternating, with the D₈ or [3^5,1,1] Coxeter group.

Cartesian coordinates

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

(±1,±1,0,0,0,0,0,0)

Images

orthographic projections

B8			B7
[16]			[14]
B6			B5
[12]			[10]
B4		B3		B2
[8]		[6]		[4]
A7		A5		A3
[8]		[6]		[4]

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
6-faces
5-faces
4-faces
Cells
Faces
Edges
Vertices
Vertex figure	{3,3,3,4}x{3}
Coxeter groups	C8, [3,3,3,3,3,3,4] D8, [3^5,1,1]
Properties	convex

Alternate names

• birectified octacross
• birectified diacosipentacontahexazetton (Acronym: bark) (Jonathan Bowers)^[2]

Cartesian coordinates

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

(±1,±1,±1,0,0,0,0,0)

Images

orthographic projections

B8			B7
[16]			[14]
B6			B5
[12]			[10]
B4		B3		B2
[8]		[6]		[4]
A7		A5		A3
[8]		[6]		[4]

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
6-faces
5-faces
4-faces
Cells
Faces
Edges
Vertices
Vertex figure	{3,3,4}x{3,3}
Coxeter groups	C8, [3,3,3,3,3,3,4] D8, [3^5,1,1]
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)^[3]

Cartesian coordinates

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

(±1,±1,±1,±1,0,0,0,0)

Images

orthographic projections

B8			B7
[16]			[14]
B6			B5
[12]			[10]
B4		B3		B2
[8]		[6]		[4]
A7		A5		A3
[8]		[6]		[4]

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, [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]
• Norman Johnson Uniform Polytopes, Manuscript (1991)
  • N.W. Johnson: The Theory of Uniform Polytopes and Honeycombs, Ph.D.
• Richard Klitzing, 8D, uniform polytopes (polyzetta) o3x3o3o3o3o3o4o - rek, o3o3x3o3o3o3o4o - bark, o3o3o3x3o3o3o4o - tark

External links

• Olshevsky, George, Cross polytope at Glossary for Hyperspace.
• Polytopes of Various Dimensions
• Multi-dimensional Glossary