Witting polytope
Schläfli symbol 3{3}3{3}3{3}3
Coxeter diagram
Cells 240 3{3}3{3}3
Faces 2160 3{3}3
Edges 2160 3{}
Vertices 240
Petrie polygon 30-gon
van Oss polygon 90 3{4}3
Shephard group L4 = 3[3]3[3]3[3]3, order 155,520
Dual polyhedron Self-dual
Properties Regular

In 4-dimensional complex geometry, the Witting polytope is a regular complex polytope, named as: 3{3}3{3}3{3}3, and Coxeter diagram . It has 240 vertices, 2160 3{} edges, 2160 3{3}3 faces, and 240 3{3}3{3}3 cells. It is self-dual. Each vertex belongs to 27 edges, 72 faces, and 27 cells, corresponding to the Hessian polyhedron vertex figure.

Symmetry

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Its symmetry by 3[3]3[3]3[3]3 or        , order 155,520.[1] It has 240 copies of      , order 648 at each cell.[2]

Structure

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The configuration matrix is:[3]  

The number of vertices, edges, faces, and cells are seen in the diagonal of the matrix. These are computed by the order of the group divided by the order of the subgroup, by removing certain complex reflections, shown with X below. The number of elements of the k-faces are seen in rows below the diagonal. The number of elements in the vertex figure, etc., are given in rows above the digonal.

L4         k-face fk f0 f1 f2 f3 k-figure Notes
L3         ( ) f0 240 27 72 27 3{3}3{3}3 L4/L3 = 216*6!/27/4! = 240
L2L1         3{ } f1 3 2160 8 8 3{3}3 L4/L2L1 = 216*6!/4!/3 = 2160
        3{3}3 f2 8 8 2160 3 3{ }
L3         3{3}3{3}3 f3 27 72 27 240 ( ) L4/L3 = 216*6!/27/4! = 240

Coordinates

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Its 240 vertices are given coordinates in  :

(0, ±ωμ, -±ων, ±ωλ)
(-±ωμ, 0, ±ων, ±ωλ)
(±ωμ, -±ων, 0, ±ωλ)
(-±ωλ, -±ωμ, -±ων, 0)
(±iωλ√3, 0, 0, 0)
(0, ±iωλ√3, 0, 0)
(0, 0, ±iωλ√3, 0)
(0, 0, 0, ±iωλ√3)

where  .

The last 6 points form hexagonal holes on one of its 40 diameters. There are 40 hyperplanes contain central 3{3}3{4}2,       figures, with 72 vertices.

Witting configuration

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Coxeter named it after Alexander Witting for being a Witting configuration in complex projective 3-space:[4]

  or  

The Witting configuration is related to the finite space PG(3,22), consisting of 85 points, 357 lines, and 85 planes.[5]

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Its 240 vertices are shared with the real 8-dimensional polytope 421,              . Its 2160 3-edges are sometimes drawn as 6480 simple edges, slightly less than the 6720 edges of 421. The 240 difference is accounted by 40 central hexagons in 421 whose edges are not included in 3{3}3{3}3{3}3.[6]

The honeycomb of Witting polytopes

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The regular Witting polytope has one further stage as a 4-dimensional honeycomb,          . It has the Witting polytope as both its facets, and vertex figure. It is self-dual, and its dual coincides with itself.[7]

Hyperplane sections of this honeycomb include 3-dimensional honeycombs        .

The honeycomb of Witting polytopes has a real representation as the 8-dimensional polytope 521,                .

Its f-vector element counts are in proportion: 1, 80, 270, 80, 1.[8] The configuration matrix for the honeycomb is:

L5           k-face fk f0 f1 f2 f3 f4 k-figure Notes
L4           ( ) f0 N 240 2160 2160 240 3{3}3{3}3{3}3 L5/L4 = N
L3L1           3{ } f1 3 80N 27 72 27 3{3}3{3}3 L5/L3L1 = 80N
L2L2           3{3}3 f2 8 8 270N 8 8 3{3}3 L5/L2L2 = 270N
L3L1           3{3}3{3}3 f3 27 72 27 80N 3 3{} L5/L3L1 = 80N
L4           3{3}3{3}3{3}3 f4 240 2160 2160 240 N ( ) L5/L4 = N

Notes

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  1. ^ Coxeter Regular Convex Polytopes, 12.5 The Witting polytope
  2. ^ Coxeter, Complex Regular Polytopes, p.134
  3. ^ Coxeter, Complex Regular polytopes, p.132
  4. ^ Alexander Witting, Ueber Jacobi'sche Functionen kter Ordnung Zweier Variabler, Mathemematische Annalen 29 (1887), 157-70, see especially p.169
  5. ^ Coxeter, Complex regular polytopes, p.133
  6. ^ Coxeter, Complex Regular Polytopes, p.134
  7. ^ Coxeter, Complex Regular Polytopes, p.135
  8. ^ Coxeter Regular Convex Polytopes, 12.5 The Witting polytope

References

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  • Coxeter, H. S. M. and Moser, W. O. J.; Generators and Relations for Discrete Groups (1965), esp pp 67–80.
  • Coxeter, H. S. M.; Regular Complex Polytopes, Cambridge University Press, second edition (1991). pp. 132–5, 143, 146, 152.
  • Coxeter, H. S. M. and Shephard, G.C.; Portraits of a family of complex polytopes, Leonardo Vol 25, No 3/4, (1992), pp 239–244 [1]