Open main menu
Demihexeract
(6-demicube)
Demihexeract ortho petrie.svg
Petrie polygon projection
Type Uniform 6-polytope
Family demihypercube
Schläfli symbol {3,33,1} = h{4,34}
s{21,1,1,1,1}
Coxeter diagrams CDel nodes 10ru.pngCDel split2.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png = CDel node h1.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png
CDel nodes 01r.pngCDel 3ab.pngCDel nodes.pngCDel split5c.pngCDel nodes.png = CDel nodes.pngCDel 3ab.pngCDel nodes.pngCDel split5c.pngCDel nodes 10l.png

CDel node h.pngCDel 2x.pngCDel node h.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png
CDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png
CDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.png
CDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 4.pngCDel node.png
CDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.pngCDel 2x.pngCDel node h.png

Coxeter symbol 131
5-faces 44 12 {31,2,1}Demipenteract graph ortho.svg
32 {34}5-simplex t0.svg
4-faces 252 60 {31,1,1}Cross graph 4.svg
192 {33}4-simplex t0.svg
Cells 640 160 {31,0,1}3-simplex t0.svg
480 {3,3}3-simplex t0.svg
Faces 640 {3}2-simplex t0.svg
Edges 240
Vertices 32
Vertex figure Rectified 5-simplex
5-simplex t1.svg
Symmetry group D6, [33,1,1] = [1+,4,34]
[25]+
Petrie polygon decagon
Properties convex

In geometry, a 6-demicube or demihexteract is a uniform 6-polytope, constructed from a 6-cube (hexeract) with alternated vertices removed. It is part of a dimensionally infinite family of uniform polytopes called demihypercubes.

E. L. Elte identified it in 1912 as a semiregular polytope, labeling it as HM6 for a 6-dimensional half measure polytope.

Coxeter named this polytope as 131 from its Coxeter diagram, with a ring on one of the 1-length branches, CDel node 1.pngCDel 3.pngCDel node.pngCDel split1.pngCDel nodes.pngCDel 3a.pngCDel nodea.pngCDel 3a.pngCDel nodea.png. It can named similarly by a 3-dimensional exponential Schläfli symbol or {3,33,1}.

Cartesian coordinatesEdit

Cartesian coordinates for the vertices of a demihexeract centered at the origin are alternate halves of the hexeract:

(±1,±1,±1,±1,±1,±1)

with an odd number of plus signs.

As a configurationEdit

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

The diagonal f-vector numbers are derived through the Wythoff construction, dividing the full group order of a subgroup order by removing one mirror at a time.[3]

D6           k-face fk f0 f1 f2 f3 f4 f5 k-figure notes
A4           ( ) f0 32 15 60 20 60 15 30 6 6 r{3,3,3,3} D6/A4 = 32*6!/5! = 32
A3A1A1           { } f1 2 240 8 4 12 6 8 4 2 {}x{3,3} D6/A3A1A1 = 32*6!/4!/2/2 = 240
A3A2           {3} f2 3 3 640 1 3 3 3 3 1 {3}v( ) D6/A3A2 = 32*6!/4!/3! = 640
A3A1           h{4,3} f3 4 6 4 160 * 3 0 3 0 {3} D6/A3A1 = 32*6!/4!/2 = 160
A3A2           {3,3} 4 6 4 * 480 1 2 2 1 {}v( ) D6/A3A2 = 32*6!/4!/3! = 480
D4A1           h{4,3,3} f4 8 24 32 8 8 60 * 2 0 { } D6/D4A1 = 32*6!/8/4!/2 = 60
A4           {3,3,3} 5 10 10 0 5 * 192 1 1 D6/A4 = 32*6!/5! = 192
D5           h{4,3,3,3} f5 16 80 160 40 80 10 16 12 * ( ) D6/D5 = 32*6!/16/5! = 12
A5           {3,3,3,3} 6 15 20 0 15 0 6 * 32 D6/A5 = 32*6!/6! = 32

ImagesEdit

orthographic projections
Coxeter plane B6
Graph  
Dihedral symmetry [12/2]
Coxeter plane D6 D5
Graph    
Dihedral symmetry [10] [8]
Coxeter plane D4 D3
Graph    
Dihedral symmetry [6] [4]
Coxeter plane A5 A3
Graph    
Dihedral symmetry [6] [4]

Related polytopesEdit

There are 47 uniform polytopes with D6 symmetry, 31 are shared by the B6 symmetry, and 16 are unique:

The 6-demicube, 131 is third in a dimensional series of uniform polytopes, expressed by Coxeter as k31 series. The fifth figure is a Euclidean honeycomb, 331, and the final is a noncompact hyperbolic honeycomb, 431. Each progressive uniform polytope is constructed from the previous as its vertex figure.

k31 dimensional figures
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] [32,3,1] [33,3,1] [34,3,1]
Order 48 720 23,040 2,903,040
Graph         - -
Name −131 031 131 231 331 431

It is also the second in a dimensional series of uniform polytopes and honeycombs, expressed by Coxeter as 13k series. The next figure is the Euclidean honeycomb 133 and the final is a noncompact hyperbolic honeycomb, 134.

13k 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] [32,3,1] [[33,3,1]] [34,3,1]
Order 48 720 23,040 2,903,040
Graph       - -
Name 13,-1 130 131 132 133 134

ReferencesEdit

  1. ^ Coxeter, Regular Polytopes, sec 1.8 Configurations
  2. ^ Coxeter, Complex Regular Polytopes, p.117
  3. ^ Klitzing, Richard. "x3o3o *b3o3o3o - hax".
  • H.S.M. Coxeter:
    • Coxeter, Regular Polytopes, (3rd edition, 1973), Dover edition, ISBN 0-486-61480-8, p.296, Table I (iii): Regular Polytopes, three regular polytopes in n-dimensions (n≥5)
    • H.S.M. Coxeter, Regular Polytopes, 3rd Edition, Dover New York, 1973, p.296, Table I (iii): Regular Polytopes, three regular polytopes in n-dimensions (n≥5)
    • 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]
  • John H. Conway, Heidi Burgiel, Chaim Goodman-Strass, The Symmetries of Things 2008, ISBN 978-1-56881-220-5 (Chapter 26. pp. 409: Hemicubes: 1n1)
  • Klitzing, Richard. "6D uniform polytopes (polypeta) x3o3o *b3o3o3o – hax".

External linksEdit