- 8-orthoplex
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8-orthoplex
Heptacross
Orthogonal projection
inside Petrie polygonType Regular 8-polytope Family orthoplex Schläfli symbol {36,4}
{35,1,1}Coxeter-Dynkin diagrams 
7-faces 256 {36} 
6-faces 1024 {35} 
5-faces 1792 {34} 
4-faces 1792 {33} 
Cells 1120 {3,3} 
Faces 448 {3} 
Edges 112 Vertices 16 Vertex figure 7-orthoplex Petrie polygon hexadecagon Coxeter groups C8, [36,4]
D8, [35,1,1]Dual 8-cube Properties convex In geometry, an 8-orthoplex, or 8-cross polytope is a regular 8-polytope with 16 vertices, 112 edges, 448 triangle faces, 1120 tetrahedron cells, 1792 5-cells 4-faces, 1792 5-faces, 1024 6-faces, and 256 7-faces.
It has two constructive forms, the first being regular with Schläfli symbol {36,4}, and the second with alternately labeled (checkerboarded) facets, with Schläfli symbol {35,1,1} or Coxeter symbol 511.
Contents
Alternate names
- Octacross, derived from combining the family name cross polytope with oct for eight (dimensions) in Greek
- Diacosipentacontahexazetton as a 256-facetted 8-polytope (polyzetton)
Construction
There are two Coxeter groups associated with the 8-cube, one regular, dual of the octeract with the C8 or [4,3,3,3,3,3,3] symmetry group, and a lower symmetry with two copies of 7-simplex facets, alternating, with the D8 or [35,1,1] symmetry group.
Images
orthographic projections B8 B7 
[16] [14] B6 B5 
[12] [10] B4 B3 B2 
[8] [6] [4] A7 A5 A3 
[8] [6] [4] Related tessellations
Related polytopes
It is a part of an infinite family of polytopes, called cross-polytopes or orthoplexes. The dual polytope is an 8-hypercube, or octeract.
It is used in its alternated form 511 with the 8-simplex to form the 521 honeycomb.
Cartesian coordinates
Cartesian coordinates for the vertices of an 8-cube, centered at the origin are
- (±1,0,0,0,0,0,0,0), (0,±1,0,0,0,0,0,0), (0,0,±1,0,0,0,0,0), (0,0,0,±1,0,0,0,0),
- (0,0,0,0,±1,0,0,0), (0,0,0,0,0,±1,0,0), (0,0,0,0,0,0,0,±1), (0,0,0,0,0,0,0,±1)
Every vertex pair is connected by an edge, except opposites.
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, editied by F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss, Wiley-Interscience Publication, 1995, ISBN 978-0-471-01003-6 [1]
- (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), x3o3o3o3o3o3o4o - ek
External links
- Olshevsky, George, Cross polytope at Glossary for Hyperspace.
- Polytopes of Various Dimensions
- Multi-dimensional Glossary
Fundamental convex regular and uniform polytopes in dimensions 2–10 Family An BCn Dn E6 / E7 / E8 / F4 / G2 Hn Regular polygon Triangle Square Hexagon Pentagon Uniform polyhedron Tetrahedron Octahedron • Cube Demicube Dodecahedron • Icosahedron Uniform polychoron 5-cell 16-cell • Tesseract Demitesseract 24-cell 120-cell • 600-cell Uniform 5-polytope 5-simplex 5-orthoplex • 5-cube 5-demicube Uniform 6-polytope 6-simplex 6-orthoplex • 6-cube 6-demicube 122 • 221 Uniform 7-polytope 7-simplex 7-orthoplex • 7-cube 7-demicube 132 • 231 • 321 Uniform 8-polytope 8-simplex 8-orthoplex • 8-cube 8-demicube 142 • 241 • 421 Uniform 9-polytope 9-simplex 9-orthoplex • 9-cube 9-demicube Uniform 10-polytope 10-simplex 10-orthoplex • 10-cube 10-demicube n-polytopes n-simplex n-orthoplex • n-cube n-demicube 1k2 • 2k1 • k21 pentagonal polytope Topics: Polytope families • Regular polytope • List of regular polytopes Categories:- 8-polytopes
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