Order-8 triangular tiling

In geometry, the order-8 triangular tiling is a regular tiling of the hyperbolic plane. It is represented by Schläfli symbol of {3,8}, having eight regular triangles around each vertex.

Uniform colorings

The half symmetry [1⁺,8,3] = [(4,3,3)] can be shown with alternating two colors of triangles:

Symmetry

Octagonal tiling with *444 mirror lines, .

From [(4,4,4)] symmetry, there are 15 small index subgroups (7 unique) by mirror removal and alternation operators. Mirrors can be removed if its branch orders are all even, and cuts neighboring branch orders in half. Removing two mirrors leaves a half-order gyration point where the removed mirrors met. In these images fundamental domains are alternately colored black and white, and mirrors exist on the boundaries between colors. Adding 3 bisecting mirrors across each fundamental domains creates 832 symmetry. The subgroup index-8 group, [(1⁺,4,1⁺,4,1⁺,4)] (222222) is the commutator subgroup of [(4,4,4)].

A larger subgroup is constructed [(4,4,4^*)], index 8, as (2*2222) with gyration points removed, becomes (*22222222).

The symmetry can be doubled to 842 symmetry by adding a bisecting mirror across the fundamental domains. The symmetry can be extended by 6, as 832 symmetry, by 3 bisecting mirrors per domain.

Small index subgroups of [(4,4,4)] (*444)

Index	1	2			4
Diagram
Coxeter	[(4,4,4)]	[(1+,4,4,4)] =	[(4,1+,4,4)] =	[(4,4,1+,4)] =	[(1+,4,1+,4,4)]	[(4+,4+,4)]
Orbifold	*444	*4242			2*222	222×
Diagram
Coxeter		[(4,4+,4)]	[(4,4,4+)]	[(4+,4,4)]	[(4,1+,4,1+,4)]	[(1+,4,4,1+,4)] =
Orbifold		4*22			2*222
Direct subgroups
Index	2	4			8
Diagram
Coxeter	[(4,4,4)]+	[(4,4+,4)]+ =	[(4,4,4+)]+ =	[(4+,4,4)]+ =	[(4,1+,4,1+,4)]+ =
Orbifold	444	4242			222222
Radical subgroups
Index	8			16
Diagram
Coxeter	[(4,4*,4)]	[(4,4,4*)]	[(4*,4,4)]	[(4,4*,4)]+	[(4,4,4*)]+	[(4*,4,4)]+
Orbifold	*22222222			22222222

Related polyhedra and tilings

The {3,3,8} honeycomb has {3,8} vertex figures.

From a Wythoff construction there are ten hyperbolic uniform tilings that can be based from the regular octagonal and order-8 triangular tilings.

Drawing the tiles colored as red on the original faces, yellow at the original vertices, and blue along the original edges, there are 10 forms.

Uniform octagonal/triangular tilings
Symmetry: [8,3], (*832)							[8,3]+ (832)	[1+,8,3] (*443)		[8,3+] (3*4)
{8,3}	t{8,3}	r{8,3}	t{3,8}	{3,8}	rr{8,3} s2{3,8}	tr{8,3}	sr{8,3}	h{8,3}	h2{8,3}	s{3,8}
								or	or
Uniform duals
V83	V3.16.16	V3.8.3.8	V6.6.8	V38	V3.4.8.4	V4.6.16	V34.8	V(3.4)3	V8.6.6	V35.4

It can also be generated from the (4 3 3) hyperbolic tilings:

See also

• Order-8 tetrahedral honeycomb
• Tilings of regular polygons
• List of uniform planar tilings
• List of regular polytopes

References

• John H. Conway, Heidi Burgiel, Chaim Goodman-Strauss, The Symmetries of Things 2008, ISBN:978-1-56881-220-5 (Chapter 19, The Hyperbolic Archimedean Tessellations)
• "Chapter 10: Regular honeycombs in hyperbolic space". The Beauty of Geometry: Twelve Essays. Dover Publications. 1999. ISBN 0-486-40919-8. 

External links

• Weisstein, Eric W.. "Hyperbolic tiling". http://mathworld.wolfram.com/HyperbolicTiling.html. 
• Weisstein, Eric W.. "Poincaré hyperbolic disk". http://mathworld.wolfram.com/PoincareHyperbolicDisk.html. 
• Hyperbolic and Spherical Tiling Gallery
• KaleidoTile 3: Educational software to create spherical, planar and hyperbolic tilings
• Hyperbolic Planar Tessellations, Don Hatch