Compound of five tetrahedra
Template:Short description Template:More sources needed
| Compound of five tetrahedra | |
|---|---|
| File:Compound of five tetrahedra.png | |
| Type | Regular compound |
| Coxeter symbol | {5,3}[5{3,3}] {3,5}Template:Sfn |
| Index | UC5, W24 |
| Elements (As a compound) |
5 tetrahedra: F = 20, E = 30, V = 20 |
| Dual compound | Self-dual |
| Symmetry group | chiral icosahedral (I) |
| Subgroup restricting to one constituent | chiral tetrahedral (T) |
The compound of five tetrahedra, also known as the chiricosahedron, is one of the five regular polyhedral compounds. This compound polyhedron is also a stellation of the regular icosahedron. It was first described by Edmund Hess in 1876.
It can be seen as a faceting of a regular dodecahedron.
As a compound
It can be constructed by arranging five tetrahedra in rotational icosahedral symmetry (I), as colored in the upper right model. It is one of five regular compounds which can be constructed from identical Platonic solids.Template:Sfn
It shares the same vertex arrangement as a regular dodecahedron.
There are two enantiomorphous forms (the same figure but having opposite chirality) of this compound polyhedron. Both forms together create the reflection symmetric compound of ten tetrahedra.
It has a density of higher than 1.
| File:Spherical compound of five tetrahedra.png As a spherical tiling |
File:CompoundOfFiveTetrahedra.png Transparent Models (Animation) |
File:Five tetrahedra.png Five interlocked tetrahedra |
As a stellation
It can also be obtained by stellating the icosahedron, and is given as Wenninger model index 24.Template:Sfn
| Stellation diagram | Stellation core | Convex hull |
|---|---|---|
| File:Compound of five tetrahedra stellation facets.svg | File:Icosahedron.png Icosahedron |
File:Dodecahedron.png Dodecahedron |
As a faceting
It is a faceting of a dodecahedron, as shown at left.
Group theory
The compound of five tetrahedra is a geometric illustration of the notion of orbits and stabilizers, as follows.
The symmetry group of the compound is the (rotational) icosahedral group I of order 60, while the stabilizer of a single chosen tetrahedron is the (rotational) tetrahedral group T of order 12, and the orbit space I/T (of order 60/12 = 5) is naturally identified with the 5 tetrahedra – the coset gT corresponds to which tetrahedron g sends the chosen tetrahedron to.
An unusual dual property
This compound is unusual, in that the dual figure is the enantiomorph of the original. If the faces are twisted to the right, then the vertices are twisted to the left. When we dualise, the faces dualise to right-twisted vertices and the vertices dualise to left-twisted faces, giving the chiral twin. Figures with this property are extremely rare.
In 4-dimensional space
The compound of five tetrahedra is related to the regular 5-cell, the 4-simplex regular 4-polytope, which is also composed of 5 regular tetrahedra. In the 5-cell the tetrahedra are bonded face-to-face such that each triangular face is shared by two tetrahedral cells.
The compound of five tetrahedra occurs embedded in 4-dimensional space, inscribed in the 120 dodecahedral cells of the 120-cell. The 120-cell is the largest and most comprehensive regular 4-polytope; the regular 5-cell is the smallest and most elemental. The 120-cell contains inscribed within itself instances of every other regular 4-polytope.Template:Sfn In each of the 120-cell's dodecahedral cells, there are two inscribed instances of the compound of 5 tetrahedra (in other words, one instance of the compound of ten tetrahedra). The 5 tetrahedra of each compound of five occur as cells of another regular 4-polytope inscribed within the 120-cell, the 600-cell, which has 600 regular tetrahedra as its cells. The 120-cell is a compound of 5 disjoint 600-cells, and each of its dodecahedral cells is a compound of 5 tetrahedral cells, one cell from each of the 5 disjoint 600-cells.
See also
Citations
References
- Script error: No such module "citation/CS1".
- Script error: No such module "citation/CS1".
- Script error: No such module "citation/CS1".
- Script error: No such module "citation/CS1".
External links
- Script error: No such module "Template wrapper".
- Metal Sculpture of Five Tetrahedra Compound
- VRML model: [1]
- Compounds of 5 and 10 Tetrahedra by Sándor Kabai, The Wolfram Demonstrations Project.
- Template:KlitzingPolytopes