Rectified 7-simplexes

7-simplex Template:CDD	Rectified 7-simplex Template:CDD
Birectified 7-simplex Template:CDD	Trirectified 7-simplex Template:CDD
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 7-polytope
Coxeter symbol	051
Schläfli symbol	r{36} = {35,1} or $\left\{\begin{array}{c}3,3,3,3,3\\ 3\end{array}\right\}$
Coxeter diagrams	Template:CDD Or Template:CDD
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. It is called 0_5,1 for its branching Coxeter-Dynkin diagram, shown as Template:CDD.

E. L. Elte identified it in 1912 as a semiregular polytope, labeling it as STemplate:Supsub.

Alternate names

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

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.

Birectified 7-simplex

Birectified 7-simplex
Type	uniform 7-polytope
Coxeter symbol	042
Schläfli symbol	2r{3,3,3,3,3,3} = {34,2} or $\left\{\begin{array}{c}3,3,3,3\\ 3,3\end{array}\right\}$
Coxeter diagrams	Template:CDD Or Template:CDD
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

E. L. Elte identified it in 1912 as a semiregular polytope, labeling it as STemplate:Supsub. It is also called 0_4,2 for its branching Coxeter-Dynkin diagram, shown as Template:CDD.

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.

Trirectified 7-simplex

Trirectified 7-simplex
Type	uniform 7-polytope
Coxeter symbol	033
Schläfli symbol	3r{36} = {33,3} or $\left\{\begin{array}{c}3,3,3\\ 3,3,3\end{array}\right\}$
Coxeter diagrams	Template:CDD Or Template:CDD
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

The trirectified 7-simplex is the intersection of two regular 7-simplexes in dual configuration.

E. L. Elte identified it in 1912 as a semiregular polytope, labeling it as STemplate:Supsub.

This polytope is the vertex figure of the 1₃₃ honeycomb. It is called 0_3,3 for its branching Coxeter-Dynkin diagram, shown as Template:CDD.

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).

Related polytopes

Isotopic uniform truncated simplices

Dim.	2	3	4	5	6	7	8
Name Coxeter	Hexagon Template:CDD = Template:CDD t{3} = {6}	Octahedron Template:CDD = Template:CDD r{3,3} = {31,1} = {3,4} $\left\{\begin{array}{c}3\\ 3\end{array}\right\}$	Decachoron Template:CDD 2t{33}	Dodecateron Template:CDD 2r{34} = {32,2} $\left\{\begin{array}{c}3,3\\ 3,3\end{array}\right\}$	Tetradecapeton Template:CDD 3t{35}	Hexadecaexon Template:CDD 3r{36} = {33,3} $\left\{\begin{array}{c}3,3,3\\ 3,3,3\end{array}\right\}$	Octadecazetton Template:CDD 4t{37}
Images
Vertex figure	( )∨( )	{ }×{ }	{ }∨{ }	{3}×{3}	{3}∨{3}	{3,3}×{3,3}	{3,3}∨{3,3}
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}
As intersecting dual simplexes	Template:CDD ∩ Template:CDD	Template:CDD ∩ Template:CDD	Template:CDD ∩ Template:CDD	Template:CDD ∩ Template:CDD	Template:CDD ∩ Template:CDD	Template:CDD ∩ Template:CDD	Template:CDD ∩ Template:CDD

Related polytopes

These polytopes are three of 71 uniform 7-polytopes with A₇ symmetry. Template:Octaexon family

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, edited by F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss, Wiley-Interscience Publication, 1995, Template:Isbn [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.
• Template:KlitzingPolytopes o3o3x3o3o3o3o - broc, o3x3o3o3o3o3o - roc, o3o3x3o3o3o3o - he

External links

• Polytopes of Various Dimensions
• Multi-dimensional Glossary