Английская Википедия:1 42 polytope

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Файл:4 21 t0 E6.svg
421
Шаблон:CDD
Файл:1 42 polytope E6 Coxeter plane.svg
142
Шаблон:CDD
Файл:2 41 t0 E6.svg
241
Шаблон:CDD
Файл:4 21 t1 E6.svg
Rectified 421
Шаблон:CDD
Файл:4 21 t4 E6.svg
Rectified 142
Шаблон:CDD
Файл:2 41 t1 E6.svg
Rectified 241
Шаблон:CDD
Файл:4 21 t2 E6.svg
Birectified 421
Шаблон:CDD
Файл:4 21 t3 E6.svg
Trirectified 421
Шаблон:CDD
Orthogonal projections in E6 Coxeter plane

In 8-dimensional geometry, the 142 is a uniform 8-polytope, constructed within the symmetry of the E8 group.

Its Coxeter symbol is 142, describing its bifurcating Coxeter-Dynkin diagram, with a single ring on the end of the 1-node sequences.

The rectified 142 is constructed by points at the mid-edges of the 142 and is the same as the birectified 241, and the quadrirectified 421.

These polytopes are part of a family of 255 (28 − 1) convex uniform polytopes in 8 dimensions, made of uniform polytope facets and vertex figures, defined by all non-empty combinations of rings in this Coxeter-Dynkin diagram: Шаблон:CDD.

142 polytope

142
Type Uniform 8-polytope
Family 1k2 polytope
Schläfli symbol {3,34,2}
Coxeter symbol 142
Coxeter diagrams Шаблон:CDD
Шаблон:CDD
7-faces 2400:
240 132Файл:Gosset 1 32 petrie.svg
2160 141Файл:Demihepteract ortho petrie.svg
6-faces 106080:
6720 122Файл:Gosset 1 22 polytope.svg
30240 131Файл:Demihexeract ortho petrie.svg
69120 {35}Файл:6-simplex t0.svg
5-faces 725760:
60480 112Файл:Demipenteract graph ortho.svg
181440 121Файл:Demipenteract graph ortho.svg
483840 {34}Файл:5-simplex t0.svg
4-faces 2298240:
241920 102Файл:4-simplex t0.svg
604800 111Файл:4-cube t3.svg
1451520 {33}Файл:4-simplex t0.svg
Cells 3628800:
1209600 101Файл:3-simplex t0.svg
2419200 {32}Файл:3-simplex t0.svg
Faces 2419200 {3}Файл:2-simplex t0.svg
Edges 483840
Vertices 17280
Vertex figure t2{36} Файл:7-simplex t2.svg
Petrie polygon 30-gon
Coxeter group E8, [34,2,1]
Properties convex

The 142 is composed of 2400 facets: 240 132 polytopes, and 2160 7-demicubes (141). Its vertex figure is a birectified 7-simplex.

This polytope, along with the demiocteract, can tessellate 8-dimensional space, represented by the symbol 152, and Coxeter-Dynkin diagram: Шаблон:CDD.

Alternate names

  • E. L. Elte (1912) excluded this polytope from his listing of semiregular polytopes, because it has more than two types of 6-faces, but under his naming scheme it would be called V17280 for its 17280 vertices.[1]
  • Coxeter named it 142 for its bifurcating Coxeter-Dynkin diagram, with a single ring on the end of the 1-node branch.
  • Diacositetracont-dischiliahectohexaconta-zetton (acronym bif) - 240-2160 facetted polyzetton (Jonathan Bowers)[2]

Coordinates

The 17280 vertices can be defined as sign and location permutations of:

All sign combinations (32): (280×32=8960 vertices)

(4, 2, 2, 2, 2, 0, 0, 0)

Half of the sign combinations (128): ((1+8+56)×128=8320 vertices)

(2, 2, 2, 2, 2, 2, 2, 2)
(5, 1, 1, 1, 1, 1, 1, 1)
(3, 3, 3, 1, 1, 1, 1, 1)

The edge length is 2Шаблон:Radic in this coordinate set, and the polytope radius is 4Шаблон:Radic.

Construction

It is created by a Wythoff construction upon a set of 8 hyperplane mirrors in 8-dimensional space.

The facet information can be extracted from its Coxeter-Dynkin diagram: Шаблон:CDD.

Removing the node on the end of the 2-length branch leaves the 7-demicube, 141, Шаблон:CDD.

Removing the node on the end of the 4-length branch leaves the 132, Шаблон:CDD.

The vertex figure is determined by removing the ringed node and ringing the neighboring node. This makes the birectified 7-simplex, 042, Шаблон:CDD.

Seen in a configuration matrix, the element counts can be derived by mirror removal and ratios of Coxeter group orders.[3]

Projections

Файл:E8 142 Petrie Projection.png
The projection of 142 to the E8 Coxeter plane (aka. the Petrie projection) with polytope radius <math>4\sqrt{2}</math> is shown below with 483,840 edges of length <math>2\sqrt{2}</math> culled 53% on the interior to only 226,444:
Файл:E8 142-3D Concentric Hulls.png
Shown in 3D projection using the basis vectors [u,v,w] giving H3 symmetry: Шаблон:Ubl The 17280 projected 142 polytope vertices are sorted and tallied by their 3D norm generating the increasingly transparent hulls for each set of tallied norms. Notice the last two outer hulls are a combination of two overlapped Dodecahedrons (40) and a Nonuniform Rhombicosidodecahedron (60).
E8
[30]
E7
[18]
E6
[12]
Файл:Gosset 1 42 polytope petrie.svg
(1)
Файл:1 42 t0 e7.svg
(1,3,6)
Файл:1 42 polytope E6 Coxeter plane.svg
(8,16,24,32,48,64,96)
[20] [24] [6]
Файл:1 42 t0 p20.svg Файл:1 42 t0 p24.svg Файл:1 42 t0 mox.svg
(1,2,3,4,5,6,7,8,10,11,12,14,16,18,19,20)

Orthographic projections are shown for the sub-symmetries of E8: E7, E6, B8, B7, B6, B5, B4, B3, B2, A7, and A5 Coxeter planes, as well as two more symmetry planes of order 20 and 24. Vertices are shown as circles, colored by their order of overlap in each projective plane.

D3 / B2 / A3
[4]
D4 / B3 / A2
[6]
D5 / B4
[8]
Файл:1 42 t0 B2.svg
(32,160,192,240,480,512,832,960)
Файл:1 42 t0 B3.svg
(72,216,432,720,864,1080)
Файл:1 42 t0 B4.svg
(8,16,24,32,48,64,96)
D6 / B5 / A4
[10]
D7 / B6
[12]
D8 / B7 / A6
[14]
Файл:1 42 t0 B5.svg Файл:1 42 t0 B6.svg Файл:1 42 t0 B7.svg
B8
[16/2]
A5
[6]
A7
[8]
Файл:1 42 t0 B8.svg Файл:1 42 t0 A5.svg Файл:1 42 t0 A7.svg

Related polytopes and honeycombs

Шаблон:1 k2 polytopes

Rectified 142 polytope

Rectified 142
Type Uniform 8-polytope
Schläfli symbol t1{3,34,2}
Coxeter symbol 0421
Coxeter diagrams Шаблон:CDD
Шаблон:CDD
7-faces 19680
6-faces 382560
5-faces 2661120
4-faces 9072000
Cells 16934400
Faces 16934400
Edges 7257600
Vertices 483840
Vertex figure {3,3,3}×{3}×{}
Coxeter group E8, [34,2,1]
Properties convex

The rectified 142 is named from being a rectification of the 142 polytope, with vertices positioned at the mid-edges of the 142. It can also be called a 0421 polytope with the ring at the center of 3 branches of length 4, 2, and 1.

Alternate names

  • 0421 polytope
  • Birectified 241 polytope
  • Quadrirectified 421 polytope
  • Rectified diacositetracont-dischiliahectohexaconta-zetton as a rectified 240-2160 facetted polyzetton (acronym buffy) (Jonathan Bowers)[4]

Construction

It is created by a Wythoff construction upon a set of 8 hyperplane mirrors in 8-dimensional space.

The facet information can be extracted from its Coxeter-Dynkin diagram: Шаблон:CDD.

Removing the node on the end of the 1-length branch leaves the birectified 7-simplex, Шаблон:CDD

Removing the node on the end of the 2-length branch leaves the birectified 7-cube, Шаблон:CDD.

Removing the node on the end of the 3-length branch leaves the rectified 132, Шаблон:CDD.

The vertex figure is determined by removing the ringed node and ringing the neighboring node. This makes the 5-cell-triangle duoprism prism, Шаблон:CDD.

Seen in a configuration matrix, the element counts can be derived by mirror removal and ratios of Coxeter group orders.[5]

Projections

Orthographic projections are shown for the sub-symmetries of B6, B5, B4, B3, B2, A7, and A5 Coxeter planes. Vertices are shown as circles, colored by their order of overlap in each projective plane.

(Planes for E8: E7, E6, B8, B7, [24] are not shown for being too large to display.)


D3 / B2 / A3
[4]
D4 / B3 / A2
[6]
D5 / B4
[8]
Файл:4 21 t4 B2.svg Файл:4 21 t4 B3.svg Файл:4 21 t4 B4.svg
D6 / B5 / A4
[10]
D7 / B6
[12]
[6]
Файл:4 21 t4 B5.svg Файл:4 21 t4 B6.svg Файл:4 21 t4 mox.svg
A5
[6]
A7
[8]
 
[20]
Файл:4 21 t4 A5.svg Файл:4 21 t4 A7.svg Файл:4 21 t4 p20.svg

See also

Notes

Шаблон:Reflist

References

  • 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, Шаблон:ISBN [1]
    • (Paper 24) H.S.M. Coxeter, Regular and Semi-Regular Polytopes III, [Math. Zeit. 200 (1988) 3-45]
  • Шаблон:KlitzingPolytopes o3o3o3x *c3o3o3o3o - bif, o3o3o3x *c3o3o3o3o - buffy

Шаблон:Polytopes

  1. Шаблон:Citation
  2. Klitzing, (o3o3o3x *c3o3o3o3o - bif)
  3. Coxeter, Regular Polytopes, 11.8 Gossett figures in six, seven, and eight dimensions, p. 202-203
  4. Klitzing, (o3o3o3x *c3o3o3o3o - buffy)
  5. Coxeter, Regular Polytopes, 11.8 Gossett figures in six, seven, and eight dimensions, p. 202-203