Order-4 dodecahedral honeycomb
| Order-4 dodecahedral honeycomb | |
|---|---|
 Perspective projection view within Beltrami-Klein model |
|
| Type | Hyperbolic regular honeycomb |
| Schläfli symbol | {5,3,4} {5,31,1} |
| Coxeter-Dynkin diagram |        |
| Cells | dodecahedron {5,3} |
| Faces | pentagon {5} |
| Edge figure | square {4} |
| Vertex figure |  octahedron |
| Cells/edge | {5,3}4 |
| Cells/vertex | {5,3}8 |
| Euler characteristic | 0 |
| Dual | Order-5 cubic honeycomb |
| Coxeter group | BH3, [5,3,4] DH3, [5,31,1] |
| Properties | Regular |
In the geometry of hyperbolic 3-space, the order-4 dodecahedral honeycomb is one of four regular space-filling tessellation (or honeycombs). Four dodecahedra exist around each edge, and 8 dodecahedra around each vertex in an octahedral arrangement. Its vertices are constructed from 3 orthogonal axes. Its dual is the order-5 cubic honeycomb.
The dihedral angle of a dodecahedron is ~116.6°, so it is impossible to fit 4 of them on an edge in Euclidean 3-space. However in hyperbolic space a properly scaled dodecahedron can be scaled so that its dihedral angles are reduced to 90 degrees, and then four fit exactly on every edge.
[edit] Related polytopes and honeycombs
It is similar to the cubic honeycomb {4,3,4} of Euclidean 3-space. Both have an octahedral vertex figure, replacing the cubic cells by dodecahedra.
There are fifteen uniform honeycombs in the [5,3,4] Coxeter group family, including this regular form.
There are eleven uniform honeycombs in the bifurcating [5,31,1] Coxeter group family, including this honeycomb in its alternated form. This construction can be represented by alternation (checkerboard) with two colors of dodecahedral cells.
There is another regular honeycomb in hyperbolic 3-space called the order-5 dodecahedral honeycomb which has 5 dodecahedra per edge.
This honeycomb is also related to the 120-cell which has 120 dodecahedra in 4-dimensional space, with 3 dodecahedra on each edge.
[edit] See also
- Convex uniform honeycombs in hyperbolic space
- Poincaré homology sphere Poincaré dodecahedral space
- Seifert–Weber space Seifert–Weber dodecahedral space
- List of regular polytopes
[edit] References
- Coxeter, Regular Polytopes, 3rd. ed., Dover Publications, 1973. ISBN 0-486-61480-8. (Tables I and II: Regular polytopes and honeycombs, pp. 294–296)
- Coxeter, The Beauty of Geometry: Twelve Essays, Dover Publications, 1999 ISBN 0-486-40919-8 (Chapter 10: Regular honeycombs in hyperbolic space, Summary tables II,III,IV,V, p212-213)
- Jeffrey R. Weeks The Shape of Space, 2nd edition ISBN 0-8247-0709-5 (Chapter 16-17: Geometries on Three-manifolds I,II) [1]
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