6-orthoplex

Summary

6-orthoplex
Hexacross
6-cube t5.svg
Orthogonal projection
inside Petrie polygon
Type Regular 6-polytope
Family orthoplex
Schläfli symbols {3,3,3,3,4}
{3,3,3,31,1}
Coxeter-Dynkin diagrams CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 4.pngCDel node.png
CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel split1.pngCDel nodes.png = CDel nodes 10r.pngCDel 3ab.pngCDel nodes.pngCDel split5c.pngCDel nodes.png
5-faces 64 {34}5-simplex t0.svg
4-faces 192 {33}4-simplex t0.svg
Cells 240 {3,3}3-simplex t0.svg
Faces 160 {3}2-simplex t0.svg
Edges 60
Vertices 12
Vertex figure 5-orthoplex
Petrie polygon dodecagon
Coxeter groups B6, [4,34]
D6, [33,1,1]
Dual 6-cube
Properties convex

In geometry, a 6-orthoplex, or 6-cross polytope, is a regular 6-polytope with 12 vertices, 60 edges, 160 triangle faces, 240 tetrahedron cells, 192 5-cell 4-faces, and 64 5-faces.

It has two constructed forms, the first being regular with Schläfli symbol {34,4}, and the second with alternately labeled (checkerboarded) facets, with Schläfli symbol {3,3,3,31,1} or Coxeter symbol 311.

It is a part of an infinite family of polytopes, called cross-polytopes or orthoplexes. The dual polytope is the 6-hypercube, or hexeract.

Alternate namesEdit

As a configurationEdit

This configuration matrix represents the 6-orthoplex. 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-orthoplex. The nondiagonal numbers say how many of the column's element occur in or at the row's element.[1][2]

 

ConstructionEdit

There are three Coxeter groups associated with the 6-orthoplex, one regular, dual of the hexeract with the C6 or [4,3,3,3,3] Coxeter group, and a half symmetry with two copies of 5-simplex facets, alternating, with the D6 or [33,1,1] Coxeter group. A lowest symmetry construction is based on a dual of a 6-orthotope, called a 6-fusil.

Name Coxeter Schläfli Symmetry Order
Regular 6-orthoplex             {3,3,3,3,4} [4,3,3,3,3] 46080
Quasiregular 6-orthoplex           {3,3,3,31,1} [3,3,3,31,1] 23040
6-fusil             {3,3,3,4}+{} [4,3,3,3,3] 7680
            {3,3,4}+{4} [4,3,3,2,4] 3072
            2{3,4} [4,3,2,4,3] 2304
            {3,3,4}+2{} [4,3,3,2,2] 1536
            {3,4}+{4}+{} [4,3,2,4,2] 768
            3{4} [4,2,4,2,4] 512
            {3,4}+3{} [4,3,2,2,2] 384
            2{4}+2{} [4,2,4,2,2] 256
            {4}+4{} [4,2,2,2,2] 128
            6{} [2,2,2,2,2] 64

Cartesian coordinatesEdit

Cartesian coordinates for the vertices of a 6-orthoplex, centered at the origin are

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

Every vertex pair is connected by an edge, except opposites.

ImagesEdit

orthographic projections
Coxeter plane B6 B5 B4
Graph      
Dihedral symmetry [12] [10] [8]
Coxeter plane B3 B2
Graph    
Dihedral symmetry [6] [4]
Coxeter plane A5 A3
Graph    
Dihedral symmetry [6] [4]

Related polytopesEdit

The 6-orthoplex can be projected down to 3-dimensions into the vertices of a regular icosahedron.[3]

2D 3D
 
Icosahedron
{3,5} =      
H3 Coxeter plane
 
6-orthoplex
{3,3,3,31,1} =          
D6 Coxeter plane
 
Icosahedron
 
6-orthoplex
This construction can be geometrically seen as the 12 vertices of the 6-orthoplex projected to 3 dimensions as the vertices of a regular icosahedron. This represents a geometric folding of the D6 to H3 Coxeter groups:  :       to      . On the left, seen by these 2D Coxeter plane orthogonal projections, the two overlapping central vertices define the third axis in this mapping. Every pair of vertices of the 6-orthoplex are connected, except opposite ones: 30 edges are shared with the icosahedron, while 30 more edges from the 6-orthoplex project to the interior of the icosahedron.

It is in a dimensional series of uniform polytopes and honeycombs, expressed by Coxeter as 3k1 series. (A degenerate 4-dimensional case exists as 3-sphere tiling, a tetrahedral hosohedron.)

3k1 dimensional figures
Space Finite Euclidean Hyperbolic
n 4 5 6 7 8 9
Coxeter
group
A3A1 A5 D6 E7  =E7+  =E7++
Coxeter
diagram
                                                                   
Symmetry [3−1,3,1] [30,3,1] [[31,3,1]]
= [4,3,3,3,3]
[32,3,1] [33,3,1] [34,3,1]
Order 48 720 46,080 2,903,040
Graph       - -
Name 31,-1 310 311 321 331 341

This polytope is one of 63 uniform 6-polytopes generated from the B6 Coxeter plane, including the regular 6-cube or 6-orthoplex.

B6 polytopes
 
β6  
t1β6
 
t2β6
 
t2γ6
 
t1γ6
 
γ6
 
t0,1β6
 
t0,2β6
 
t1,2β6
 
t0,3β6
 
t1,3β6
 
t2,3γ6
 
t0,4β6
 
t1,4γ6
 
t1,3γ6
 
t1,2γ6
 
t0,5γ6
 
t0,4γ6
 
t0,3γ6
 
t0,2γ6
 
t0,1γ6
 
t0,1,2β6
 
t0,1,3β6
 
t0,2,3β6
 
t1,2,3β6
 
t0,1,4β6
 
t0,2,4β6
 
t1,2,4β6
 
t0,3,4β6
 
t1,2,4γ6
 
t1,2,3γ6
 
t0,1,5β6
 
t0,2,5β6
 
t0,3,4γ6
 
t0,2,5γ6
 
t0,2,4γ6
 
t0,2,3γ6
 
t0,1,5γ6
 
t0,1,4γ6
 
t0,1,3γ6
 
t0,1,2γ6
 
t0,1,2,3β6
 
t0,1,2,4β6
 
t0,1,3,4β6
 
t0,2,3,4β6
 
t1,2,3,4γ6
 
t0,1,2,5β6
 
t0,1,3,5β6
 
t0,2,3,5γ6
 
t0,2,3,4γ6
 
t0,1,4,5γ6
 
t0,1,3,5γ6
 
t0,1,3,4γ6
 
t0,1,2,5γ6
 
t0,1,2,4γ6
 
t0,1,2,3γ6
 
t0,1,2,3,4β6
 
t0,1,2,3,5β6
 
t0,1,2,4,5β6
 
t0,1,2,4,5γ6
 
t0,1,2,3,5γ6
 
t0,1,2,3,4γ6
 
t0,1,2,3,4,5γ6

ReferencesEdit

  • 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 [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. 1966
  • Klitzing, Richard. "6D uniform polytopes (polypeta) x3o3o3o3o4o - gee".
Specific
  1. ^ Coxeter, Regular Polytopes, sec 1.8 Configurations
  2. ^ Coxeter, Complex Regular Polytopes, p.117
  3. ^ Quasicrystals and Geometry, Marjorie Senechal, 1996, Cambridge University Press, p64. 2.7.1 The I6 crystal

External linksEdit

  • Olshevsky, George. "Cross polytope". Glossary for Hyperspace. Archived from the original on 4 February 2007.
  • Polytopes of Various Dimensions
  • Multi-dimensional Glossary
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