Regular 4-polytope

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In mathematics, a regular 4-polytope is a 4-polytope that is both regular. They are the four-dimensional analogs of the regular polyhedra in three dimensions and the regular polygons in two dimensions.

Regular 4-polytopes were first described by the Swiss mathematician Ludwig Schläfli in the mid-19th century, although the full set were not discovered until later.

There are six convex and ten star regular 4-polytopes, giving a total of sixteen.

History[edit]

The convex 4-polytopes were first described by the Swiss mathematician Ludwig Schläfli in the mid-19th century. Schläfli discovered that there are precisely six such figures.

Schläfli also found four of the regular star 4-polytopes; (the grand 120-cell, great stellated 120-cell, grand 600-cell, and great grand stellated 120-cell). He skipped the remaining six because he would not allow forms that failed the Euler characteristic on cells or vertex figures (for zero-hole tori: F − E + V = 2). That excludes cells and vertex figures as {5,5/2}, and {5/2,5}.

Edmund Hess (1843–1903) published the complete list in his 1883 German book Einleitung in die Lehre von der Kugelteilung mit besonderer Berücksichtigung ihrer Anwendung auf die Theorie der Gleichflächigen und der gleicheckigen Polyeder.

Construction[edit]

The existence of a regular 4-polytope \{p,q,r\} is constrained by the existence of the regular polyhedra \{p,q\}, \{q,r\} which form its cells and a dihedral angle constraint

\sin(\frac{\pi}{p}) \sin(\frac{\pi}{r}) < \cos(\frac{\pi}{q}).

to ensure that the cells meet to form a closed 3-surface.

The six convex and ten star polytopes described are the only solutions to these constraints.

There are four nonconvex Schläfli symbols {p,q,r} that have valid cells {p,q} and vertex figures {q,r}, and pass the dihedral test, but fail to produce finite figures: {3,5/2,3}, {4,3,5/2}, {5/2,3,4}, {5/2,3,5/2}.

Regular convex 4-polytopes[edit]

The tesseract is one of 6 convex regular 4-polytopes

The regular convex 4-polytopes are the four-dimensional analogs of the Platonic solids in three dimensions and the convex regular polygons in two dimensions.

Five of them may be thought of as close analogs of the Platonic solids. There is one additional figure, the 24-cell, which has no close three-dimensional equivalent.

Each convex regular 4-polytope is bounded by a set of 3-dimensional cells which are all Platonic solids of the same type and size. These are fitted together along their respective faces in a regular fashion.

Properties[edit]

The following tables lists some properties of the six convex regular 4-polytopes. The symmetry groups of these 4-polytopes are all Coxeter groups and given in the notation described in that article. The number following the name of the group is the order of the group.

Names Family Schläfli
Coxeter
Vertices Edges Faces Cells Vertex
figures
Dual Symmetry group
5-cell
pentachoron
pentatope
4-simplex
simplex
(n-simplex)
{3,3,3}
CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png
5 10 10
{3}
5
{3,3}
{3,3} (self-dual) A4
[3,3,3]
120
8-cell
octachoron
tesseract
4-cube
hypercube
(n-cube)
{4,3,3}
CDel node 1.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png
16 32 24
{4}
8
{4,3}
{3,3} 16-cell B4
[4,3,3]
384
16-cell
hexadecachoron
4-orthoplex
cross-polytope
(n-orthoplex)
{3,3,4}
CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 4.pngCDel node.png
8 24 32
{3}
16
{3,3}
{3,4} 8-cell B4
[4,3,3]
384
24-cell
icositetrachoron
octaplex
polyoctahedron
{3,4,3}
CDel node 1.pngCDel 3.pngCDel node.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.png
24 96 96
{3}
24
{3,4}
{4,3} (self-dual) F4
[3,4,3]
1152
120-cell
hecatonicosachoron
dodecaplex
polydodecahedron
dodecahedral
pentagonal polytope
(n-pentagonal polytope)
{5,3,3}
CDel node 1.pngCDel 5.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png
600 1200 720
{5}
120
{5,3}
{3,3} 600-cell H4
[5,3,3]
14400
600-cell
hexacosichoron
tetraplex
polytetrahedron
icosahedral
pentagonal polytope
(n-pentagonal polytope)
{3,3,5}
CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 5.pngCDel node.png
120 720 1200
{3}
600
{3,3}
{3,5} 120-cell H4
[5,3,3]
14400

John Conway advocates the names simplex, orthoplex, tesseract, octaplex or polyoctahedron, dodecaplex or polydodecahedron, and tetraplex or polytetrahedron.[1]

Norman Johnson advocates the names n-cell, or pentachoron, tesseract or octachoron, hexadecachoron, icositetrachoron, hecatonicosachoron (or dodecacontachoron), and hexacosichoron, coining the term polychoron being a 4D analogy to the 3D polyhedron, and 2D polygon, expressed from the Greek roots poly ("many") and choros ("room" or "space").[2][3]

The Euler characteristic for all 4-polytopes is zero, we have the 4-dimensional analog of Euler's polyhedral formula:

N_0 - N_1 + N_2 - N_3 = 0\,

where Nk denotes the number of k-faces in the polytope (a vertex is a 0-face, an edge is a 1-face, etc.).

Visualization[edit]

The following table shows some 2-dimensional projections of these 4-polytopes. Various other visualizations can be found in the external links below. The Coxeter-Dynkin diagram graphs are also given below the Schläfli symbol.

A4 = [3,3,3] BC4 = [4,3,3] F4 = [3,4,3] H4 = [5,3,3]
5-cell 8-cell 16-cell 24-cell 120-cell 600-cell
{3,3,3} {4,3,3} {3,3,4} {3,4,3} {5,3,3} {3,3,5}
CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png CDel node 1.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 4.pngCDel node.png CDel node 1.pngCDel 3.pngCDel node.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node.png CDel node 1.pngCDel 5.pngCDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.png CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 5.pngCDel node.png
Wireframe 2D orthographic projections inside Petrie polygons.
4-simplex t0.svg 4-cube t0.svg 4-cube t3.svg 24-cell t0 F4.svg 120-cell graph H4.svg 600-cell graph H4.svg
Solid 3D orthographic projections
Tetrahedron.png
tetrahedral
envelope

(cell/vertex-centered)
Hexahedron.png
cubic envelope
(cell-centered)
16-cell ortho cell-centered.png
Cubic envelope
(cell-centered)
Ortho solid 24-cell.png
cuboctahedral
envelope

(cell-centered)
Ortho solid 120-cell.png
truncated rhombic
triacontahedron
envelope

(cell-centered)
Ortho solid 600-cell.png
Pentakis icosidodecahedral
envelope

(vertex-centered)
Wireframe Schlegel diagrams (Perspective projection)
Schlegel wireframe 5-cell.png
Cell-centered
Schlegel wireframe 8-cell.png
Cell-centered
Schlegel wireframe 16-cell.png
Cell-centered
Schlegel wireframe 24-cell.png
Cell-centered
Schlegel wireframe 120-cell.png
Cell-centered
Schlegel wireframe 600-cell vertex-centered.png
Vertex-centered
Wireframe stereographic projections (3-sphere)
Stereographic polytope 5cell.png Stereographic polytope 8cell.png Stereographic polytope 16cell.png Stereographic polytope 24cell.png Stereographic polytope 120cell.png Stereographic polytope 600cell.png

Regular star (Schläfli–Hess) 4-polytopes[edit]

The great grand 120-cell, one of ten Schläfli–Hess polychora by orthographic projection.

The Schläfli–Hess polychora are the complete set of 10 regular self-intersecting star polychora (four-dimensional polytopes). They are named in honor of their discoverers: Ludwig Schläfli and Edmund Hess. Each is represented by a Schläfli symbol {p,q,r} in which one of the numbers is 5/2. They are thus analogous to the regular nonconvex Kepler–Poinsot polyhedra.

Names[edit]

Their names given here were given by John Conway, extending Cayley's names for the Kepler–Poinsot polyhedra: along with stellated and great, he adds a grand modifier. Conway offered these operational definitions:

  1. stellation – replaces edges by longer edges in same lines. (Example: a pentagon stellates into a pentagram)
  2. greatening – replaces the faces by large ones in same planes. (Example: an icosahedron greatens into a great icosahedron)
  3. aggrandizement – replaces the cells by large ones in same 3-spaces. (Example: a 600-cell aggrandizes into a grand 600-cell)

Symmetry[edit]

All ten polychora have [3,3,5] (H4) hexacosichoric symmetry. They are generated from 6 related Goursat tetrahedra rational-order symmetry groups: [3,5,5/2], [5,5/2,5], [5,3,5/2], [5/2,5,5/2], [5,5/2,3], and [3,3,5/2].

Each group has 2 regular star-polychora, except for two groups which are self-dual, having only one. So there are 4 dual-pairs and 2 self-dual forms among the ten regular star polychora.

Properties[edit]

Note:

The cells (polyhedra), their faces (polygons), the polygonal edge figures and polyhedral vertex figures are identified by their Schläfli symbols.

Name
(Bowers acronym)
Wireframe Solid Schläfli
{p, q,r}
Coxeter–Dynkin
Cells
{p, q}
Faces
{p}
Edges
{r}
Vertices
{q, r}
Density χ Dual
{r, q,p}
Icosahedral 120-cell
(or faceted 600-cell)
(or icosaplex)
(fix)
Schläfli-Hess polychoron-wireframe-3.png Ortho solid 007-uniform polychoron 35p-t0.png {3,5,5/2}
CDel node 1.pngCDel 3.pngCDel node.pngCDel 5.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.png
120
{3,5}
Icosahedron.png
1200
{3}
Triangle.Equilateral.svg
720
{5/2}
Pentagram.svg
120
{5,5/2}
Great dodecahedron.png
4 480 Small stellated 120-cell
Small stellated 120-cell
(sishi)
Schläfli-Hess polychoron-wireframe-2.png Ortho solid 010-uniform polychoron p53-t0.png {5/2,5,3}
CDel node.pngCDel 3.pngCDel node.pngCDel 5.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node 1.png
120
{5/2,5}
Small stellated dodecahedron.png
720
{5/2}
Pentagram.svg
1200
{3}
Triangle.Equilateral.svg
120
{5,3}
Dodecahedron.png
4 −480 Icosahedral 120-cell
Great 120-cell
(gohi)
Schläfli-Hess polychoron-wireframe-3.png Ortho solid 008-uniform polychoron 5p5-t0.png {5,5/2,5}
CDel node 1.pngCDel 5.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.pngCDel 5.pngCDel node.png
120
{5,5/2}
Great dodecahedron.png
720
{5}
Pentagon.svg
720
{5}
Pentagon.svg
120
{5/2,5}
Small stellated dodecahedron.png
6 0 Self-dual
Grand 120-cell
(gahi)
Schläfli-Hess polychoron-wireframe-3.png Ortho solid 009-uniform polychoron 53p-t0.png {5,3,5/2}
CDel node 1.pngCDel 5.pngCDel node.pngCDel 3.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.png
120
{5,3}
Dodecahedron.png
720
{5}
Pentagon.svg
720
{5/2}
Pentagram.svg
120
{3,5/2}
Great icosahedron.png
20 0 Great stellated 120-cell
Great stellated 120-cell
(gishi)
Schläfli-Hess polychoron-wireframe-4.png Ortho solid 012-uniform polychoron p35-t0.png {5/2,3,5}
CDel node.pngCDel 5.pngCDel node.pngCDel 3.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node 1.png
120
{5/2,3}
Great stellated dodecahedron.png
720
{5/2}
Pentagram.svg
720
{5}
Pentagon.svg
120
{3,5}
Icosahedron.png
20 0 Grand 120-cell
Grand stellated 120-cell
(gashi)
Schläfli-Hess polychoron-wireframe-4.png Ortho solid 013-uniform polychoron p5p-t0.png {5/2,5,5/2}
CDel node 1.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.pngCDel 5.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.png
120
{5/2,5}
Small stellated dodecahedron.png
720
{5/2}
Pentagram.svg
720
{5/2}
Pentagram.svg
120
{5,5/2}
Great dodecahedron.png
66 0 Self-dual
Great grand 120-cell
(gaghi)
Schläfli-Hess polychoron-wireframe-2.png Ortho solid 011-uniform polychoron 53p-t0.png {5,5/2,3}
CDel node 1.pngCDel 5.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.pngCDel 3.pngCDel node.png
120
{5,5/2}
Great dodecahedron.png
720
{5}
Pentagon.svg
1200
{3}
Triangle.Equilateral.svg
120
{5/2,3}
Great stellated dodecahedron.png
76 −480 Great icosahedral 120-cell
Great icosahedral 120-cell
(or great faceted 600-cell)
(gofix)
Schläfli-Hess polychoron-wireframe-4.png Ortho solid 014-uniform polychoron 3p5-t0.png {3,5/2,5}
CDel node.pngCDel 5.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.pngCDel 3.pngCDel node 1.png
120
{3,5/2}
Great icosahedron.png
1200
{3}
Triangle.Equilateral.svg
720
{5}
Pentagon.svg
120
{5/2,5}
Small stellated dodecahedron.png
76 480 Great grand 120-cell
Grand 600-cell
(gax)
Schläfli-Hess polychoron-wireframe-4.png Ortho solid 015-uniform polychoron 33p-t0.png {3,3,5/2}
CDel node 1.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node.png
600
{3,3}
Tetrahedron.png
1200
{3}
Triangle.Equilateral.svg
720
{5/2}
Pentagram.svg
120
{3,5/2}
Great icosahedron.png
191 0 Great grand stellated 120-cell
Great grand stellated 120-cell
(gogishi)
Schläfli-Hess polychoron-wireframe-1.png Ortho solid 016-uniform polychoron p33-t0.png {5/2,3,3}
CDel node.pngCDel 3.pngCDel node.pngCDel 3.pngCDel node.pngCDel 5.pngCDel rat.pngCDel d2.pngCDel node 1.png
120
{5/2,3}
Great stellated dodecahedron.png
720
{5/2}
Pentagram.svg
1200
{3}
Triangle.Equilateral.svg
600
{3,3}
Tetrahedron.png
191 0 Grand 600-cell

See also[edit]

References[edit]

Citations[edit]

  1. ^ Conway, 2008, Chapter 26, Higher Still
  2. ^ "Convex and abstract polytopes", Programme and abstracts, MIT, 2005
  3. ^ Johnson (2015), Chapter 11, Section 11.5 Spherical Coxeter groups

Bibliography[edit]

  • H. S. M. Coxeter, Introduction to Geometry, 2nd ed., John Wiley & Sons Inc., 1969. ISBN 0-471-50458-0.
  • H. S. M. Coxeter, Regular Polytopes, 3rd. ed., Dover Publications, 1973. ISBN 0-486-61480-8.
  • D. M. Y. Sommerville, An Introduction to the Geometry of n Dimensions. New York, E. P. Dutton, 1930. 196 pp. (Dover Publications edition, 1958) Chapter X: The Regular Polytopes
  • John H. Conway, Heidi Burgiel, Chaim Goodman-Strass, The Symmetries of Things 2008, ISBN 978-1-56881-220-5
  • Edmund Hess, (1883) Einleitung in die Lehre von der Kugelteilung mit besonderer Berücksichtigung ihrer Anwendung auf die Theorie der Gleichflächigen und der gleicheckigen Polyeder [1].
  • Edmund Hess Uber die regulären Polytope höherer Art, Sitzungsber Gesells Beförderung gesammten Naturwiss Marburg, 1885, 31-57
  • 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 [2]
    • (Paper 10) H.S.M. Coxeter, Star Polytopes and the Schlafli Function f(α,β,γ) [Elemente der Mathematik 44 (2) (1989) 25–36]
  • H. S. M. Coxeter, Regular Complex Polytopes, 2nd. ed., Cambridge University Press 1991. ISBN 978-0-521-39490-1. [3]
  • Peter McMullen and Egon Schulte, Abstract Regular Polytopes, 2002, PDF

External links[edit]