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List of isotoxal polyhedra and tilings

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In geometry, isotoxal polyhedra and tilings are defined by the property that they have symmetries taking any edge to any other edge.[1] Polyhedra with this property can also be called "edge-transitive", but they should be distinguished from edge-transitive graphs, where the symmetries are combinatorial rather than geometric.

Regular polyhedra are isohedral (face-transitive), isogonal (vertex-transitive), and isotoxal (edge-transitive).

Quasiregular polyhedra are isogonal and isotoxal, but not isohedral; their duals are isohedral and isotoxal, but not isogonal.

The dual of an isotoxal polyhedron is also an isotoxal polyhedron. (See the Dual polyhedron article.)

Convex isotoxal polyhedra

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The dual of a convex polyhedron is also a convex polyhedron.[2]

There are nine convex isotoxal polyhedra based on the Platonic solids: the five (regular) Platonic solids, the two (quasiregular) common cores of dual Platonic solids, and their two duals.

The vertex figures of the quasiregular forms are (squares or) rectangles; the vertex figures of the duals of the quasiregular forms are (equilateral triangles and equilateral triangles, or) equilateral triangles and squares, or equilateral triangles and regular pentagons.

Form Regular Dual regular Quasiregular Quasiregular dual
Wythoff symbol q | 2 p p | 2 q 2 | p q  
Vertex configuration pq qp p.q.p.q
p=3
q=3
Tetrahedron
{3,3}

3 | 2 3
Tetrahedron
{3,3}

3 | 2 3
Tetratetrahedron
(Octahedron)

2 | 3 3
Cube
(Rhombic hexahedron)
p=4
q=3
Cube
{4,3}

3 | 2 4
Octahedron
{3,4}

4 | 2 3
Cuboctahedron

2 | 3 4
Rhombic dodecahedron
p=5
q=3
Dodecahedron
{5,3}

3 | 2 5
Icosahedron
{3,5}

5 | 2 3
Icosidodecahedron

2 | 3 5
Rhombic triacontahedron

Isotoxal star-polyhedra

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The dual of a non-convex polyhedron is also a non-convex polyhedron.[2] (By contraposition.)

There are ten non-convex isotoxal polyhedra based on the quasiregular octahedron, cuboctahedron, and icosidodecahedron: the five (quasiregular) hemipolyhedra based on the quasiregular octahedron, cuboctahedron, and icosidodecahedron, and their five (infinite) duals:

Form Quasiregular Quasiregular dual
p=3
q=3
Tetrahemihexahedron
Tetrahemihexacron
p=4
q=3
Cubohemioctahedron
Hexahemioctacron

Octahemioctahedron
Octahemioctacron (visually indistinct from Hexahemioctacron) (*)
p=5
q=3
Small icosihemidodecahedron
Small icosihemidodecacron (visually indistinct from Small dodecahemidodecacron) (*)

Small dodecahemidodecahedron
Small dodecahemidodecacron

(*) Faces, edges, and intersection points are the same; only, some other of these intersection points, not at infinity, are considered as vertices.

There are sixteen non-convex isotoxal polyhedra based on the Kepler–Poinsot polyhedra: the four (regular) Kepler–Poinsot polyhedra, the six (quasiregular) common cores of dual Kepler–Poinsot polyhedra (including four hemipolyhedra), and their six duals (including four (infinite) hemipolyhedron-duals):

Form Regular Dual regular Quasiregular Quasiregular dual
Wythoff symbol q | 2 p p | 2 q 2 | p q  
Vertex configuration pq qp p.q.p.q
p=5/2
q=3
Great stellated dodecahedron
{5/2,3}


3 | 2 5/2


Great icosahedron
{3,5/2}


5/2 | 2 3


Great icosidodecahedron
 

2 | 3 5/2
Great rhombic triacontahedron

Great icosihemidodecahedron
Great icosihemidodecacron

Great dodecahemidodecahedron
Great dodecahemidodecacron
p=5/2
q=5
Small stellated dodecahedron
{5/2,5}


5 | 2 5/2


Great dodecahedron
{5,5/2}


5/2 | 2 5


Dodecadodecahedron
 

2 | 5 5/2
Medial rhombic triacontahedron

Small icosihemidodecahedron
Small dodecahemicosacron

Great dodecahemidodecahedron
Great dodecahemicosacron

Finally, there are six other non-convex isotoxal polyhedra: the three quasiregular ditrigonal (3 | p q) star polyhedra, and their three duals:

Quasiregular Quasiregular dual
3 | p q  

Great ditrigonal icosidodecahedron
3/2 | 3 5
Great triambic icosahedron

Ditrigonal dodecadodecahedron
3 | 5/3 5
Medial triambic icosahedron

Small ditrigonal icosidodecahedron
3 | 5/2 3
Small triambic icosahedron

Isotoxal tilings of the Euclidean plane

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There are at least 5 polygonal tilings of the Euclidean plane that are isotoxal. (The self-dual square tiling recreates itself in all four forms.)

Regular Dual regular Quasiregular Quasiregular dual

Hexagonal tiling
{6,3}

6 | 2 3
Triangular tiling
{3,6}

3 | 2 3
Trihexagonal tiling

2 | 3 6
Rhombille tiling

Square tiling
{4,4}

4 | 2 4
Square tiling
{4,4}

2 | 4 4
Square tiling
{4,4}

4 | 2 4
Square tiling
{4,4}

Isotoxal tilings of the hyperbolic plane

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There are infinitely many isotoxal polygonal tilings of the hyperbolic plane, including the Wythoff constructions from the regular hyperbolic tilings {p,q}, and non-right (p q r) groups.

Here are six (p q 2) families, each with two regular forms, and one quasiregular form. All have rhombic duals of the quasiregular form, but only one is shown:

[p,q] {p,q} {q,p} r{p,q} Dual r{p,q}
Coxeter-Dynkin
[7,3]
{7,3}
{3,7}
r{7,3}
[8,3]
{8,3}
{3,8}
r{8,3}
[5,4]
{5,4}
{4,5}
r{5,4}
[6,4]
{6,4}
{4,6}
r{6,4}
[8,4]
{8,4}
{4,8}
r{8,3}
[5,5]
{5,5}
{5,5}
r{5,5}

Here's 3 example (p q r) families, each with 3 quasiregular forms. The duals are not shown, but have isotoxal hexagonal and octagonal faces.

Coxeter-Dynkin
(4 3 3)
3 | 4 3
3 | 4 3
4 | 3 3
(4 4 3)
4 | 4 3
3 | 4 4
4 | 4 3
(4 4 4)
4 | 4 4
4 | 4 4
4 | 4 4

Isotoxal tilings of the sphere

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All isotoxal polyhedra listed above can be made as isotoxal tilings of the sphere.

In addition as spherical tilings, there are two other families which are degenerate as polyhedra. Even ordered hosohedron can be semiregular, alternating two lunes, and thus isotoxal:

References

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  1. ^ Peter R. Cromwell, Polyhedra, Cambridge University Press 1997, ISBN 0-521-55432-2, p. 371
  2. ^ a b "duality". maths.ac-noumea.nc. Retrieved 2020-10-01.
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