Rectified 7-simplexes

7-simplex	Rectified 7-simplex
Birectified 7-simplex	Trirectified 7-simplex
Orthogonal projections in A7 Coxeter plane

In seven-dimensional geometry, a rectified 7-simplex is a convex uniform 7-polytope, being a rectification of the regular 7-simplex.

There are four unique degrees of rectifications, including the zeroth, the 7-simplex itself. Vertices of the rectified 7-simplex are located at the edge-centers of the 7-simplex. Vertices of the birectified 7-simplex are located in the triangular face centers of the 7-simplex. Vertices of the trirectified 7-simplex are located in the tetrahedral cell centers of the 7-simplex.

Rectified 7-simplex

Rectified 7-simplex
Type	uniform polyexon
Schläfli symbol	r{3,3,3,3,3,3}
Coxeter-Dynkin diagrams	Or
6-faces	16
5-faces	84
4-faces	224
Cells	350
Faces	336
Edges	168
Vertices	28
Vertex figure	6-simplex prism
Petrie polygon	Octagon
Coxeter group	A7, [36], order 40320
Properties	convex

The rectified 7-simplex is the edge figure of the 2₅₁ honeycomb.

Alternate names

• Rectified octaexon (Acronym: roc) (Jonathan Bowers)

Coordinates

The vertices of the rectified 7-simplex can be most simply positioned in 8-space as permutations of (0,0,0,0,0,0,1,1). This construction is based on facets of the rectified 8-orthoplex.

Images

orthographic projections

Ak Coxeter plane	A7	A6	A5
Graph
Dihedral symmetry	[8]	[7]	[6]
Ak Coxeter plane	A4	A3	A2
Graph
Dihedral symmetry	[5]	[4]	[3]

Birectified 7-simplex

Birectified 7-simplex
Type	uniform polyexon
Schläfli symbol	2r{3,3,3,3,3,3}
Coxeter-Dynkin diagrams	Or
6-faces	16: 8 r{35} 8 2r{35}
5-faces	112: 28 {34} 56 r{34} 28 2r{34}
4-faces	392: 168 {33} (56+168) r{33}
Cells	770: (420+70) {3,3} 280 {3,4}
Faces	840: (280+560) {3}
Edges	420
Vertices	56
Vertex figure	{3}x{3,3,3}
Coxeter group	A7, [36], order 40320
Properties	convex

Alternate names

• Birectified octaexon (Acronym: broc) (Jonathan Bowers)

Coordinates

The vertices of the birectified 7-simplex can be most simply positioned in 8-space as permutations of (0,0,0,0,0,1,1,1). This construction is based on facets of the birectified 8-orthoplex.

Images

orthographic projections

Ak Coxeter plane	A7	A6	A5
Graph
Dihedral symmetry	[8]	[7]	[6]
Ak Coxeter plane	A4	A3	A2
Graph
Dihedral symmetry	[5]	[4]	[3]

Trirectified 7-simplex

Trirectified 7-simplex
Type	uniform polyexon
Schläfli symbol	3r{36}
Coxeter-Dynkin diagrams	Or
6-faces	16 2r{35}
5-faces	112
4-faces	448
Cells	980
Faces	1120
Edges	560
Vertices	70
Vertex figure	{3,3}x{3,3}
Coxeter group|A7×2, [[36]], order 80640
Properties	convex, isotopic

This polytope is the vertex figure of the 1₃₃ honeycomb.

Alternate names

• Hexadecaexon (Acronym: he) (Jonathan Bowers)

Coordinates

The vertices of the trirectified 7-simplex can be most simply positioned in 8-space as permutations of (0,0,0,0,1,1,1,1). This construction is based on facets of the trirectified 8-orthoplex.

The trirectified 7-simplex is the intersection of two regular 7-simplices in dual configuration. This characterization yields simple coordinates for the vertices of a trirectified 7-simplex in 8-space: the 70 distinct permutations of (1,1,1,1,−1,−1,−1,-1).

Images

orthographic projections

Ak Coxeter plane	A7	A6	A5
Graph
Dihedral symmetry	[8]	[[7]]	[6]
Ak Coxeter plane	A4	A3	A2
Graph
Dihedral symmetry	[[5]]	[4]	[[3]]

Related polytopes

Isotopic uniform truncated simplices

Dim.	2	3	4	5	6	7	8
Name	t{3} Hexagon	r{3,3} Octahedron	2t{3,3,3} Decachoron	2r{3,3,3,3} Dodecateron	3t{3,3,3,3,3} Tetradecapeton	3r{3,3,3,3,3,3} Hexadecaexon	4t{3,3,3,3,3,3,3} Octadecazetton
Coxeter diagram
Images
Facets		{3}	t{3,3}	r{3,3,3}	2t{3,3,3,3}	2r{3,3,3,3,3}	3t{3,3,3,3,3,3}

Related polytopes

These polytopes are three of 71 uniform 7-polytopes with A₇ symmetry.

t0	t1	t2	t3	t0,1	t0,2	t1,2	t0,3
t1,3	t2,3	t0,4	t1,4	t2,4	t0,5	t1,5	t0,6
t0,1,2	t0,1,3	t0,2,3	t1,2,3	t0,1,4	t0,2,4	t1,2,4	t0,3,4
t1,3,4	t2,3,4	t0,1,5	t0,2,5	t1,2,5	t0,3,5	t1,3,5	t0,4,5
t0,1,6	t0,2,6	t0,3,6	t0,1,2,3	t0,1,2,4	t0,1,3,4	t0,2,3,4	t1,2,3,4
t0,1,2,5	t0,1,3,5	t0,2,3,5	t1,2,3,5	t0,1,4,5	t0,2,4,5	t1,2,4,5	t0,3,4,5
t0,1,2,6	t0,1,3,6	t0,2,3,6	t0,1,4,6	t0,2,4,6	t0,1,5,6	t0,1,2,3,4	t0,1,2,3,5
t0,1,2,4,5	t0,1,3,4,5	t0,2,3,4,5	t1,2,3,4,5	t0,1,2,3,6	t0,1,2,4,6	t0,1,3,4,6	t0,2,3,4,6
t0,1,2,5,6	t0,1,3,5,6	t0,1,2,3,4,5	t0,1,2,3,4,6	t0,1,2,3,5,6	t0,1,2,4,5,6	t0,1,2,3,4,5,6

See also

• List of A7 polytopes

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
    • (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, 7D, uniform polytopes (polyexa) o3o3x3o3o3o3o - broc, o3x3o3o3o3o3o - roc, o3o3x3o3o3o3o - he

External links

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