The euclidean plane can be only tiled regularly by triangles, squares or hexagons. But what about other geometries with constant curvature? How to tile the sphere or the hyperbolic plane by regular polygons? After a short introduction to the Poincaré model of the hyperbolic plane, its regular tilings are discussed with illustrative examples from the work of M.C. Escher.
1. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling the hyperbolic plane - long
version
Daniel Czegel
Eotvos Lorand University, Budapest
ICPS, Heidelberg
August 14, 2014
Daniel Czegel Tiling the hyperbolic plane - long version
2. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Daniel Czegel Tiling the hyperbolic plane - long version
3. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Definition of Gaussian curvature
1
4. nd a normal vector N
Daniel Czegel Tiling the hyperbolic plane - long version
5. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Definition of Gaussian curvature
1
6. nd a normal vector N
2 rotate the normal plane
containing N
Daniel Czegel Tiling the hyperbolic plane - long version
7. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Definition of Gaussian curvature
1
8. nd a normal vector N
2 rotate the normal plane
containing N
3 intersection of the surface
and the normal plane: a
plane curve, curvature:
= 1R
Daniel Czegel Tiling the hyperbolic plane - long version
9. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Definition of Gaussian curvature
1
10. nd a normal vector N
2 rotate the normal plane
containing N
3 intersection of the surface
and the normal plane: a
plane curve, curvature:
= 1R
4 Gaussian curvature of the
surface:
K(r) = min(r) max (r)
Daniel Czegel Tiling the hyperbolic plane - long version
11. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Definition of Gaussian curvature
1
12. nd a normal vector N
2 rotate the normal plane
containing N
3 intersection of the surface
and the normal plane: a
plane curve, curvature:
= 1R
4 Gaussian curvature of the
surface:
K(r) = min(r) max (r)
5 sign!
Daniel Czegel Tiling the hyperbolic plane - long version
13. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Theorema Egregium
Does K(r) change if we wrap, bend, twist (i.e. change the
embedding in the 3 dim space)?
aniel Czegel Tiling the hyperbolic plane - long version
D
14. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Theorema Egregium
Does K(r) change if we wrap, bend, twist (i.e. change the
embedding in the 3 dim space)?
Theorema Egregium (Great Theorem): No!
aniel Czegel Tiling the hyperbolic plane - long version
D
15. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Theorema Egregium
Does K(r) change if we wrap, bend, twist (i.e. change the
embedding in the 3 dim space)?
Theorema Egregium (Great Theorem): No!
Gaussian curvature is an intrinsic measure of the surface!
aniel Czegel Tiling the hyperbolic plane - long version
D
16. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Theorema Egregium
Does K(r) change if we wrap, bend, twist (i.e. change the
embedding in the 3 dim space)?
Theorema Egregium (Great Theorem): No!
Gaussian curvature is an intrinsic measure of the surface!
In a 2 dimensional Universe, K fully determines how
spacetime curves: GR, Einstein eqs.:
R
R
2
g + g =
8G
c4 T
aniel Czegel Tiling the hyperbolic plane - long version
D
17. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Theorema Egregium
Does K(r) change if we wrap, bend, twist (i.e. change the
embedding in the 3 dim space)?
Theorema Egregium (Great Theorem): No!
Gaussian curvature is an intrinsic measure of the surface!
In a 2 dimensional Universe, K fully determines how
spacetime curves: GR, Einstein eqs.:
R
R
2
g + g =
8G
c4 T
In 2 dim:
R = f (K; g); R = 2K
Daniel Czegel Tiling the hyperbolic plane - long version
18. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Cylinder, Oloid
) a surface can be unfolded without distortion , K 0
aniel Czegel Tiling the hyperbolic plane - long version
D
19. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Cylinder, Oloid
) a surface can be unfolded without distortion , K 0
cylinder:
max =
1
R
; min =
1
1
= 0 ) K 0
aniel Czegel Tiling the hyperbolic plane - long version
D
20. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Cylinder, Oloid
) a surface can be unfolded without distortion , K 0
cylinder:
max =
1
R
; min =
1
1
= 0 ) K 0
nontrivial example: oloid: convex hull of two perpendicular
circles
aniel Czegel Tiling the hyperbolic plane - long version
D
21. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Cylinder, Oloid
) a surface can be unfolded without distortion , K 0
cylinder:
max =
1
R
; min =
1
1
= 0 ) K 0
nontrivial example: oloid: convex hull of two perpendicular
circles
every point of its surface touches the
oor during rolling!
Daniel Czegel Tiling the hyperbolic plane - long version
22. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
sphere: K =?
aniel Czegel Tiling the hyperbolic plane - long version
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23. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
sphere: K =?
K 1
R2 0, a model of elliptic geometry;
straight lines=geodesics: great circles
aniel Czegel Tiling the hyperbolic plane - long version
D
24. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
sphere: K =?
K 1
R2 0, a model of elliptic geometry;
straight lines=geodesics: great circles
What is the sum of angles in a triangle?
Daniel Czegel Tiling the hyperbolic plane - long version
25. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
sphere: K =?
K 1
R2 0, a model of elliptic geometry;
straight lines=geodesics: great circles
What is the sum of angles in a triangle?
Daniel Czegel Tiling the hyperbolic plane - long version
26. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
i) =
3
2
; A =
2
R2 ii) = 3; A = 2R2
aniel Czegel Tiling the hyperbolic plane - long version
D
27. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
i) =
3
2
; A =
2
R2 ii) = 3; A = 2R2
Generally?
A = ( )R2 ) KA =
aniel Czegel Tiling the hyperbolic plane - long version
D
28. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
i) =
3
2
; A =
2
R2 ii) = 3; A = 2R2
Generally?
A = ( )R2 ) KA =
The sum of angles is size-independent: only if K = 0
(euclidean geometry)
aniel Czegel Tiling the hyperbolic plane - long version
D
29. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Spherical triangles
i) =
3
2
; A =
2
R2 ii) = 3; A = 2R2
Generally?
A = ( )R2 ) KA =
The sum of angles is size-independent: only if K = 0
(euclidean geometry)
elliptic geometry:
KA 0 )
Daniel Czegel Tiling the hyperbolic plane - long version
30. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Stereographic projection
sphere: K6= 0 ) cannot be unfolded:
there is no sphere ! plane map that preserves both distance
and angle!
aniel Czegel Tiling the hyperbolic plane - long version
D
31. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Stereographic projection
sphere: K6= 0 ) cannot be unfolded:
there is no sphere ! plane map that preserves both distance
and angle!
We have to choose; e.g.: preserves angle (conformal), but
does not preserve distance: stereographic projection
aniel Czegel Tiling the hyperbolic plane - long version
D
32. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Stereographic projection
sphere: K6= 0 ) cannot be unfolded:
there is no sphere ! plane map that preserves both distance
and angle!
We have to choose; e.g.: preserves angle (conformal), but
does not preserve distance: stereographic projection
unit sphere, equator plane, project from the north pole Daniel Czegel Tiling the hyperbolic plane - long version
33. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Properties of stereographic projection
aniel Czegel Tiling the hyperbolic plane - long version
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34. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Properties of stereographic projection
northern (southern) hemisphere7! outside (inside) of the unit
circle (north pole7! 1)
aniel Czegel Tiling the hyperbolic plane - long version
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35. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Properties of stereographic projection
northern (southern) hemisphere7! outside (inside) of the unit
circle (north pole7! 1)
circle7! circle
aniel Czegel Tiling the hyperbolic plane - long version
D
36. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Properties of stereographic projection
northern (southern) hemisphere7! outside (inside) of the unit
circle (north pole7! 1)
circle7! circle
special case: geodetic (straight line)=great circle7! circle
Daniel Czegel Tiling the hyperbolic plane - long version
37. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Metric induced by stereographic projection
The spherical geometry can be modeled on a plane
aniel Czegel Tiling the hyperbolic plane - long version
D
38. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Metric induced by stereographic projection
The spherical geometry can be modeled on a plane
Do not forget: this model does not preserve distance, instead,
the metric:
ds2 = (dx2 + dy2)
4
(1 + x2 + y2)2
aniel Czegel Tiling the hyperbolic plane - long version
D
39. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Metric induced by stereographic projection
The spherical geometry can be modeled on a plane
Do not forget: this model does not preserve distance, instead,
the metric:
ds2 = (dx2 + dy2)
4
(1 + x2 + y2)2
metric tensor:
g = (x; y)
1 0
0 1
) isotropic scaling ) conformal (angle-preserving)
aniel Czegel Tiling the hyperbolic plane - long version
D
40. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Metric induced by stereographic projection
The spherical geometry can be modeled on a plane
Do not forget: this model does not preserve distance, instead,
the metric:
ds2 = (dx2 + dy2)
4
(1 + x2 + y2)2
metric tensor:
g = (x; y)
1 0
0 1
) isotropic scaling ) conformal (angle-preserving)
distance on the sphere, if (0; 0) ! 1 on the plane?
aniel Czegel Tiling the hyperbolic plane - long version
D
41. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Metric induced by stereographic projection
The spherical geometry can be modeled on a plane
Do not forget: this model does not preserve distance, instead,
the metric:
ds2 = (dx2 + dy2)
4
(1 + x2 + y2)2
metric tensor:
g = (x; y)
1 0
0 1
) isotropic scaling ) conformal (angle-preserving)
distance on the sphere, if (0; 0) ! 1 on the plane?
Z 1
0
ds =
Z 1
0
2
1 + x2 dx =
Daniel Czegel Tiling the hyperbolic plane - long version
42. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
The Earth
The image of the Earth under stereographic projection from the
south pole:
Daniel Czegel Tiling the hyperbolic plane - long version
43. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic geometry
Is K 0 (negative curvature) possible at a point?
aniel Czegel Tiling the hyperbolic plane - long version
D
44. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic geometry
Is K 0 (negative curvature) possible at a point?
Saddle point: min 0; max 0
aniel Czegel Tiling the hyperbolic plane - long version
D
45. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic geometry
Is K 0 (negative curvature) possible at a point?
Saddle point: min 0; max 0
Hyperbolic plane: saddle points everywhere! (e.g. K 1)
aniel Czegel Tiling the hyperbolic plane - long version
D
46. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic geometry
Is K 0 (negative curvature) possible at a point?
Saddle point: min 0; max 0
Hyperbolic plane: saddle points everywhere! (e.g. K 1)
Can you imagine it? Is it possible to embed it into a 3 dim
euclidean space?
Daniel Czegel Tiling the hyperbolic plane - long version
47. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic paper
Cut equilateral triangles
aniel Czegel Tiling the hyperbolic plane - long version
D
48. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic paper
Cut equilateral triangles
At every vertex, glue 7 (instead of 6) triangles to each other!
aniel Czegel Tiling the hyperbolic plane - long version
D
49. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic paper
Cut equilateral triangles
At every vertex, glue 7 (instead of 6) triangles to each other!
aniel Czegel Tiling the hyperbolic plane - long version
D
50. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic paper
Cut equilateral triangles
At every vertex, glue 7 (instead of 6) triangles to each other!
What happens, if 5 triangles are glued at a vertex?
aniel Czegel Tiling the hyperbolic plane - long version
D
51. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic paper
Cut equilateral triangles
At every vertex, glue 7 (instead of 6) triangles to each other!
What happens, if 5 triangles are glued at a vertex?
Icosahedron!
Daniel Czegel Tiling the hyperbolic plane - long version
52. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic triangles
Sum of angles in a triangle?
aniel Czegel Tiling the hyperbolic plane - long version
D
53. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic triangles
Sum of angles in a triangle?
elliptic euclidean case:
KA =
aniel Czegel Tiling the hyperbolic plane - long version
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54. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic triangles
Sum of angles in a triangle?
elliptic euclidean case:
KA =
good news: it is also valid for K 0!
aniel Czegel Tiling the hyperbolic plane - long version
D
55. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic triangles
Sum of angles in a triangle?
elliptic euclidean case:
KA =
good news: it is also valid for K 0!
A 0 ) KA 0 )
aniel Czegel Tiling the hyperbolic plane - long version
D
56. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic triangles
Sum of angles in a triangle?
elliptic euclidean case:
KA =
good news: it is also valid for K 0!
A 0 ) KA 0 )
special case: K = 1
A =
aniel Czegel Tiling the hyperbolic plane - long version
D
57. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic triangles
Sum of angles in a triangle?
elliptic euclidean case:
KA =
good news: it is also valid for K 0!
A 0 ) KA 0 )
special case: K = 1
A =
Despite the hyperbolic plane is in
58. nite, no triangle can have
larger area than !!
Daniel Czegel Tiling the hyperbolic plane - long version
59. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Poincare model of the hyperbolic plane
K6= 0 ) There is no distance-preserving AND
angle-preserving map to the euclidean plane
aniel Czegel Tiling the hyperbolic plane - long version
D
60. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Poincare model of the hyperbolic plane
K6= 0 ) There is no distance-preserving AND
angle-preserving map to the euclidean plane
Poincare model: angle preserving, but not distance preserving
(like the stereographic projection)
aniel Czegel Tiling the hyperbolic plane - long version
D
61. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Poincare model of the hyperbolic plane
K6= 0 ) There is no distance-preserving AND
angle-preserving map to the euclidean plane
Poincare model: angle preserving, but not distance preserving
(like the stereographic projection)
in
62. nite hyperbolic plane ! unit disc
aniel Czegel Tiling the hyperbolic plane - long version
D
63. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Poincare model of the hyperbolic plane
K6= 0 ) There is no distance-preserving AND
angle-preserving map to the euclidean plane
Poincare model: angle preserving, but not distance preserving
(like the stereographic projection)
in
65. nity7! edge of the unit disk
aniel Czegel Tiling the hyperbolic plane - long version
D
66. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Poincare model of the hyperbolic plane
K6= 0 ) There is no distance-preserving AND
angle-preserving map to the euclidean plane
Poincare model: angle preserving, but not distance preserving
(like the stereographic projection)
in
68. nity7! edge of the unit disk
geodesics (straight lines)7! circles that meet the edge of
the unit disc at 90
aniel Czegel Tiling the hyperbolic plane - long version
D
69. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Poincare model of the hyperbolic plane
K6= 0 ) There is no distance-preserving AND
angle-preserving map to the euclidean plane
Poincare model: angle preserving, but not distance preserving
(like the stereographic projection)
in
71. nity7! edge of the unit disk
geodesics (straight lines)7! circles that meet the edge of
the unit disc at 90
parallel lines7! not intersecting such circles
Daniel Czegel Tiling the hyperbolic plane - long version
72. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Poincare model of the hyperbolic plane
Daniel Czegel Tiling the hyperbolic plane - long version
73. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Ideal triangles
Triangles with largest area?
aniel Czegel Tiling the hyperbolic plane - long version
D
74. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Ideal triangles
Triangles with largest area?
A =
aniel Czegel Tiling the hyperbolic plane - long version
D
75. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Ideal triangles
Triangles with largest area?
A =
largest: if = 0 ( , =
76. =
= 0): How does it look like?
aniel Czegel Tiling the hyperbolic plane - long version
D
77. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Ideal triangles
Triangles with largest area?
A =
largest: if = 0 ( , =
78. =
= 0): How does it look like?
Figure 1 : Ideal triangles having all verices at in
79. nity. Note that
these triangles are congruent (having the same area A = )!
Daniel Czegel Tiling the hyperbolic plane - long version
80. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic metric
Metric?
aniel Czegel Tiling the hyperbolic plane - long version
D
81. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic metric
Metric?
ds2 = (dx2 + dy2)
4
(1(x2 + y2))2
(compare with stereographic projection!)
aniel Czegel Tiling the hyperbolic plane - long version
D
82. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic metric
Metric?
ds2 = (dx2 + dy2)
4
(1(x2 + y2))2
(compare with stereographic projection!)
again: isotropic scaling ) angle-preserving
aniel Czegel Tiling the hyperbolic plane - long version
D
83. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic metric
Metric?
ds2 = (dx2 + dy2)
4
(1(x2 + y2))2
(compare with stereographic projection!)
again: isotropic scaling ) angle-preserving
Near the edge (x2 + y2 1): ds2 dx2 + dy2
aniel Czegel Tiling the hyperbolic plane - long version
D
84. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic metric
Metric?
ds2 = (dx2 + dy2)
4
(1(x2 + y2))2
(compare with stereographic projection!)
again: isotropic scaling ) angle-preserving
Near the edge (x2 + y2 1): ds2 dx2 + dy2
center ! edge in the Poincare model: 1 distance in the
hyperbolic plane!
Z 1
0
ds =
Z 1
0
2
1 x2 dx = 1
Daniel Czegel Tiling the hyperbolic plane - long version
85. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Figure 2 : Hyperbolic man takes a walk to in
87. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Schlafli-symbol
Regular tiling: tiling by i) congruent regular poligons (n-gons),
ii) at every vertex, m poligons meet
aniel Czegel Tiling the hyperbolic plane - long version
D
88. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Schlafli-symbol
Regular tiling: tiling by i) congruent regular poligons (n-gons),
ii) at every vertex, m poligons meet
Euclidean plane?
aniel Czegel Tiling the hyperbolic plane - long version
D
89. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Schlafli-symbol
Regular tiling: tiling by i) congruent regular poligons (n-gons),
ii) at every vertex, m poligons meet
Euclidean plane?
aniel Czegel Tiling the hyperbolic plane - long version
D
90. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Schlafli-symbol
Regular tiling: tiling by i) congruent regular poligons (n-gons),
ii) at every vertex, m poligons meet
Euclidean plane?
Schla
i-symbol: fn;mg
aniel Czegel Tiling the hyperbolic plane - long version
D
91. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Schlafli-symbol
Regular tiling: tiling by i) congruent regular poligons (n-gons),
ii) at every vertex, m poligons meet
Euclidean plane?
Schla
i-symbol: fn;mg
Any relationship between these three Schla
i-symbols?
aniel Czegel Tiling the hyperbolic plane - long version
D
92. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Schlafli-symbol
Regular tiling: tiling by i) congruent regular poligons (n-gons),
ii) at every vertex, m poligons meet
Euclidean plane?
Schla
i-symbol: fn;mg
Any relationship between these three Schla
i-symbols?
1
n
+
1
m
=
1
2
There is no other such n;m 2 N , no other regular
euclidean tiling
Daniel Czegel Tiling the hyperbolic plane - long version
93. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
Regular tilings on the sphere? (assume n;m 3, i.e.
nondegenrate cases)
aniel Czegel Tiling the hyperbolic plane - long version
D
94. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
Regular tilings on the sphere? (assume n;m 3, i.e.
nondegenrate cases)
n = 3; m = 3 ?
aniel Czegel Tiling the hyperbolic plane - long version
D
95. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
Regular tilings on the sphere? (assume n;m 3, i.e.
nondegenrate cases)
n = 3; m = 3 ?
A blown tetrahedron!
Daniel Czegel Tiling the hyperbolic plane - long version
96. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
Regular tilings on the sphere? (assume n;m 3, i.e.
nondegenrate cases)
n = 3; m = 3 ?
A blown tetrahedron!
Daniel Czegel Tiling the hyperbolic plane - long version
97. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
f4; 3g ?
aniel Czegel Tiling the hyperbolic plane - long version
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98. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
f4; 3g ?
A cube:
aniel Czegel Tiling the hyperbolic plane - long version
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99. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
f4; 3g ?
A cube:
f3; 4g; f3; 5g; f5; 3g ?
aniel Czegel Tiling the hyperbolic plane - long version
D
100. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
f4; 3g ?
A cube:
f3; 4g; f3; 5g; f5; 3g ?
Octahedron, icosahedron, dodecahedron.
Daniel Czegel Tiling the hyperbolic plane - long version
101. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
Any more?
aniel Czegel Tiling the hyperbolic plane - long version
D
102. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
Any more?
No. Why?
aniel Czegel Tiling the hyperbolic plane - long version
D
103. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Tiling on the sphere
Any more?
No. Why?
1
n
+
1
m
1
2
only for these
105. ve Platonic solids
Daniel Czegel Tiling the hyperbolic plane - long version
106. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic tiling
Hyperbolic tiling?
aniel Czegel Tiling the hyperbolic plane - long version
D
107. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic tiling
m
n
Hyperbolic tiling?
If 1+ 1
2
1aniel Czegel Tiling the hyperbolic plane - long version
D
108. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic tiling
m
n
Hyperbolic tiling?
If 1+ 1
2
1How many such tilings?
aniel Czegel Tiling the hyperbolic plane - long version
D
109. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic tiling
m
n
Hyperbolic tiling?
If 1+ 1
2
1How many such tilings?
In
111. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic tiling
m
n
Hyperbolic tiling?
If 1+ 1
2
1How many such tilings?
In
112. nite!
Figure 4 : f3; 7g Figure 5 : f7; 3g
Daniel Czegel Tiling the hyperbolic plane - long version
113. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic tiling
n or m can even be in
117. =
= 0 ) A =
Figure 7 : f1; 3g,
aperiogon
Daniel Czegel Tiling the hyperbolic plane - long version
118. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Hyperbolic tiling
Or both!
Figure 8 : f1;1g
Daniel Czegel Tiling the hyperbolic plane - long version
119. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Classification of regular tilings
Figure 9 : Classi
120. cation of regular tilings
Daniel Czegel Tiling the hyperbolic plane - long version
121. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Figure 10 : M.C. Escher
Figure 11 : H.S.M.
Coxeter
Daniel Czegel Tiling the hyperbolic plane - long version
122. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Figure 12 : Escher's Circle Limit I. (1958)
Daniel Czegel Tiling the hyperbolic plane - long version
123. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Figure 13 : Circle Limit I.: nonregular tiling of the hyperbolic plane
(m = 4 and 6)
Daniel Czegel Tiling the hyperbolic plane - long version
124. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Any regular tiling?
aniel Czegel Tiling the hyperbolic plane - long version
D
125. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Any regular tiling?
Figure 14 : Escher's Circle Limit III. (1959).
aniel Czegel Tiling the hyperbolic plane - long version
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126. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Any regular tiling?
Figure 14 : Escher's Circle Limit III. (1959).
Schla
i symbol?
Daniel Czegel Tiling the hyperbolic plane - long version
127. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
Figure 15 : Schla
i symbol of Circle Limit III.: f8; 3g!
Daniel Czegel Tiling the hyperbolic plane - long version
128. Gaussian curvature
Elliptic geometry
Hyperbolic geometry
Tiling
M.C. Escher's work
References
Weeks, J. R. (2001). The shape of space. CRC press.
Dirnbock, H., Stachel, H. (1997). The development of the
oloid. Journal for Geometry and Graphics, 1(2), 105-118.
http://aleph0.clarku.edu/
~djoyce/poincare/poincare.html
http://en.wikipedia.org/wiki/
Uniform_tilings_in_hyperbolic_plane
http://euler.slu.edu/escher/index.php/
Math_and_the_Art_of_M._C._Escher
http://www.reed.edu/reed_magazine/march2010/
features/capturing_infinity/3.html
Thank You!
Daniel Czegel Tiling the hyperbolic plane - long version