Rectified tesseract explained

bgcolor=#e7dcc3 align=center colspan=3	Rectified tesseract
bgcolor=#ffffff align=center colspan=3	Schlegel diagram Centered on cuboctahedron tetrahedral cells shown
Type	Uniform 4-polytope
Schläfli symbol	r = \left\{\begin{array}{l} 4 \\ 3 , 3 \end{array}\right\} 2r h3
Coxeter-Dynkin diagrams	=
Cells	24	8 (3.4.3.4) 16 (3.3.3)
Faces	88	64 24
Edges	96
Vertices	32
Vertex figure	(Elongated equilateral-triangular prism)
Symmetry group	B4 [3,3,4], order 384 D4 [3<sup>1,1,1</sup>], order 192
Properties	convex, edge-transitive
Uniform index	10 11 12

In geometry, the rectified tesseract, rectified 8-cell is a uniform 4-polytope (4-dimensional polytope) bounded by 24 cells: 8 cuboctahedra, and 16 tetrahedra. It has half the vertices of a runcinated tesseract, with its construction, called a runcic tesseract.

It has two uniform constructions, as a rectified 8-cell r and a cantellated demitesseract, rr, the second alternating with two types of tetrahedral cells.

E. L. Elte identified it in 1912 as a semiregular polytope, labeling it as tC₈.

Construction

The rectified tesseract may be constructed from the tesseract by truncating its vertices at the midpoints of its edges.

The Cartesian coordinates of the vertices of the rectified tesseract with edge length 2 is given by all permutations of:

( 0 , \pm\sqrt{ 2 }, \pm\sqrt{ 2 }, \pm\sqrt{ 2 })

Projections

In the cuboctahedron-first parallel projection of the rectified tesseract into 3-dimensional space, the image has the following layout:

• The projection envelope is a cube.
• A cuboctahedron is inscribed in this cube, with its vertices lying at the midpoint of the cube's edges. The cuboctahedron is the image of two of the cuboctahedral cells.
• The remaining 6 cuboctahedral cells are projected to the square faces of the cube.
• The 8 tetrahedral volumes lying at the triangular faces of the central cuboctahedron are the images of the 16 tetrahedral cells, two cells to each image.

Alternative names

• Rit (Jonathan Bowers: for rectified tesseract)
• Ambotesseract (Neil Sloane & John Horton Conway)
• Rectified tesseract/Runcic tesseract (Norman W. Johnson)
  • Runcic 4-hypercube/8-cell/octachoron/4-measure polytope/4-regular orthotope
  • Rectified 4-hypercube/8-cell/octachoron/4-measure polytope/4-regular orthotope

Related uniform polytopes

Tesseract 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, http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471010030.html
    • (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. (1966)