NTNU Norwegian University of Science and Technology Faculty of Information Technology and Electrical Engineering Department of Mathematical Sciences
Max Lunde Hauge
Cantor Minimal Systems
Bachelor’s project in Mathematical Sciences Supervisor: Eduardo Ortega Esparza
May 2021
Bachelor ’s pr oject
Max Lunde Hauge
Cantor Minimal Systems
Bachelor’s project in Mathematical Sciences Supervisor: Eduardo Ortega Esparza
May 2021
Norwegian University of Science and Technology
Faculty of Information Technology and Electrical Engineering Department of Mathematical Sciences
c
⇥ C
C
⇥
{0, 1}N
i
(⇥,)) (+,⇢)
⇥
C
R
C
C
[0, 1] ⇢ R C
⇠0 =[0, 1] ⇠= ⇢ C
= 1
⇠0= [0, 1],
⇠1=⇠0\
✓1 3,2
3
◆
=
0,1
3 [
2 3, 1 , ...
⇠= = ⇠= 1
3 [
✓2
3 +⇠= 1 3
◆ .
C= Ÿ1
==1
⇠=.
⇠= 2= 1/3=
0, 1 2 C
1 C
3,23 2 C
C
(00. . .0=) = 2N
(0=) 0=
0 1 (0=) =
= 0= 2 {0, 1}= (0=)
(0=) 2{0, 1}N
0 1
|A| < 1
’1 :=0
0A: = 0 1 A. A < 1
’= :=0
0A: =0
✓1 A=+1 1 A
◆ .
G 2C
’1
==1
20=
3= 0= 2{0, 1}.
< 2 N < 1 ⇠< < <
⇥
⇠< ⇠<
<
G 2 C
’<
==1
20= 3=
| {z }
403
+
’1
==<+1
20= 3=
| {z }
) 08;
0= 2{0, 1}.
0= 0= =1 =
’1
==<+1
20=
3= 2
’1
==<+1
1 3=
!
=2
’1
==0
1 3=
’<
==0
1 3=
! ,
2 1 1 13
1 13 <+1 1 13
!
=2 1+ ( 1) + 13 <+1
2 3
! ,
3
✓1 3
◆<+1
= 1 3<.
⇠<
G G 2⇠< <
C=—1
<=1⇠<
’1
==1
20=
3= 0= 2{0, 1}.
0= = 0 = 0= = 1
=
0, 1 2 C
’1
==1
2·0 3= =0,
’1
==1
2·1 3= =2·
1 3
1 13 =1.
G 2C
G C
G
= = 4
01 = 1 02 =0 03 =1 04 =0
’4
==1
20=
3= = 2·1
31 + 2·0
32 + 2·1
33 + 2·0 34 = 20
27.
0= = =4
= =4 0= = =4
1/34
C ✓ [0, 1] ✓ R R
( ✓ R ✓ = [0,1] =(0,1)
✓( ) =1 0.
C 2=
1/3=
⇥
1
3 +2· 1
9 +4· 1
27 +8· 1
81 + · · ·=
’1
==1
2= 1 3= .
’1
==1
2= 1 3= =
’1
==1
2= 1·3 = = 1 3
1 1 23
!
=1.
1 C
1 C
C
C (0=) 2{0, 1}N
! C
! =C !
(0=) (1=) ...
N (G=)
!
! (U=)
!
(0=) 2! U0 2 (U=)
00 2 (0=) U0 =
( 1 00 =0, 0 00 =1.
U0<00 (U=) < (0=) (1=) 2!
U1 2 (U=) 10 2 (1=)
U1 =
( 1 11 =0, 0 11 =1.
U1 <11 (U=) < (1=) (G=) 2!
(U=) (G=) 2! !
(U=)
! ! (U=) !
(V=) 8 !
C C
C
⇥3 #
0 ! 1 30
1 ! 3 31
2 ! 9 32
3 ! 27 33
C G ! 2 3G
C
0 1
C ⇢ [0, 1]
[0, 3] C
C
⇥
2=3G G = log 2log 3 ' 0.631
C
C
1 2 + 1
6+ 1
18 + · · ·= 1 2+
’1
==1
2 2⇤3= = 1
2 +
’1
==1
1 3=. 1
⇠0 =
1 2 +
’1
==1
0=
3= 0= 2{0, 1}.
C
g
g
⇥
C
⇥ R
R
- 3 3 :-⇥- ! R
" - 3 (-,3) 3
3(G,~) >0 3(G,~) =0 G =~ 3(G,~) =3(~,G) G,~ 2-
3(G,I) 63(G,~) +3(~,I) G,~,I 2- R
3(0,1) = |0 1| 3
0,1 2 - 3(0,1) = 0 0 = 1 3(0,1) > 0 0,1 2 R
0,1,2 2R
R R
(-,3) (0:):1=0 2-
A > 0 # 2N <,=>#
3(0=,0<) <A.
" = (-,3)
- -
R R
(-,3) G 2- n > 0
n G n -
B(G;n) ={~ 2- |3(G,~) <n}.
(R,3) (G n;G+n)
G n
(-,3) ( ✓-
G 2( n B(G;n) ✓(
{ U} U 2N
* =–
U2N U 0 2 U ✓*
02* n B ✓ U ✓* 0 ⌫ ✓*
*
0,. . ., V V 2N
+ =—V
:=0 : 02* 0
: n B ✓ : 0: V
n
n =minn0,. . .,nV B(0,n) ✓ B(0,n:) B(0,n) ✓+ +
(-,3) ( ✓ - G 2-
( B(G;n) ( G
(-,3) ( ✓- G 2(
( (
(-,3) G 2- n > 0
n G n -
B(G;n) ={~ 2R |3(G,~)6n}.
(-,3) ( ✓ -
( G (
( " = (-,3)
(0:) ( (0:) - ( ✓- "
G 2- ( ( =(
G 2( (
⇥
8 ✓ -
Ÿ
82 8
!2
⌘ÿ
82
( 8)2 ÿ
82 8
!2
⌘ Ÿ
82
( 8)2.
C
R C ⇢ R
(-,3) ( ✓ -
(-,3) ( ✓- !
( ( ( ( ✓ -
( =( [!.
( (0,1) ( = (0,1)[! = [0,1]
( =( (
(-,3) ( ✓ - (
(2 (2 ✓-
(2 ={0 2- |08(}.
( (2
( (2
( ( ✓ - G 2 (2 n
G (2 G 2(
n B ✓$
G 2$2
& & ✓- &
G 2&2 G 8& &2
n G & B ✓&2 $2
' ✓ - ('2)2 = '
(-,3) ( ✓ - ( -
( =-
(-,3) (-,3) (-, ¯3)
5 :- ! - 3¯(5(G),5(~)) =3(G,~) G,~ 2- 5(-) ={5(G) :G 2-} -
R C
(C,3) G 2C
C
3 R 0,1 2 C 3 : C⇥C! R
3
3(0,1) =3
’1
==1
20=
3= ,
’1
==1
21=
3=
!
=
’1
==1
2|0= 1=| 3= 0=,1= 2 {0, 1}.
3
G 2 C B(G;n) ~ 2 C
n G ~
n G
1/3< < 2N n
1
3= 1 <n 31<
n > 0 = 2N G 2C
G n = 31= ~ 2 C 3(G,~) < 31= G
= G ~
G 2 C = 2 N n = 31= B(G;31=) = ~ 2C |3(G,~) < 31= G = Õ1
==02G=
3=
~ =Õ1
==0 2~= 3=
’1
==1
2|G= ~=|
3= =
’<
==1
2|G= ~=| 3=
| {z }
403
+
’1
==<+1
2|G= ~=| 3=
| {z }
) 08;
.
1/3< n
n = 1/3< < n
⇥
1/3<
= G ~
1/3<
(-,3) ( ✓ -
A > 0 3(0,1) < A 0,1 2 ( ( (-,3)
(-,3) ( ✓ - (
( (
( ✓ R (
R
C C
[0,1] C
1 < |A| [0, 1]
3(0,1) 6 1 < A C
C ⇢ [0, 1] ⇢ R
⇤
(-,3) ( ✓ - (
02(
[2,3] 2 <3
G 2⇠1 ⇠1
⇠1 =
0,1
3 [
2 3, 1 G1 2C\⇠1 G1 <G
|G G1| 1/31 = 2 N
⇠= G= 2 C\⇠= G= < G
|G G=| 1/3= C
(-,3) (,& ✓ -
(,& ( \& (\&
(-,3) ' ✓ - '=([&
( & ' '
0,1 2' 0 2
1 2⌫ '= [⌫
C C
:,; 2 C
: 2 ; 2! [! ✓⇠? ⇠? ✓⇠=
:,;
⇠=
:,;
⇠=
C
R
C
⇥
- T T ( ✓ -
-
- ; T
* T * T
⇥
* T * T
(-,T )
- B T - ⌫ ✓-
G 2- ⌫ 2B G 2⌫
D 2 T G 2D ⌫ 2B G 2⌫ ⌫ ✓D
- B T
⌫ 2B T -
⌫ 2B T *
T G 2* ⌫ 2B G 2⌫ * =–
G2* ⌫ B
(-,3) n
C
B ={B(G;n) |G 2-,n > 0}.
- . 5 :- !.
* ⇢. 5 1(*) -
- . 5 :- !.
5 5
- . - .
5 5
⇥
⇥
0 1
C - ={0, 1}N 0 1
- {0, 1}
- = {0,. . .,? 1}N ? 2
⇥
- T - T
- T -
T ;,- ✓ -
T -
G 2-
- -
? 2N ={0, 1, 2,. . .,? 1} =
N ={ }
< 2N < ={ < 2N }
⇤ =–1
<=1 < ={ < 2N }.
G 2 = ~ 2 < =,< 2N
G ~ G ~ G~ =+<
G~ =G ~ 2 =+<.
G~ <~G
G 2 = ~ 2 = G =G0G1G2. . .G=
~ =~0~1~2. . .~< G,~
G~ =G0. . .G=~0. . .~<,
~G =~0. . .~=G0. . .G<.
⇥
I 2 N I=I0I1. . .I8. . . G,I
GI =G0. . .G=I0. . .I8. . .,
IG =I0. . .I8. . . .G0. . .G=.
G 2 = ~ 2 < =,< 2N < >=
G ~ I 2 < = ~ =GI
G 2 = = ~ 2 N
G ~ 2 N
- =÷ -8. -
B = n÷
*8 |*8 ✓-8 *8 =-8 8 o
.
*8 = -8
={0,. . .,? 1} G 2
N
l l 2 ⇤ /(l) N
/(l) = l 2 ⇤,G 2 N |lG 2 N ,
={ l}.
/(l)
÷N
{0,. . .,? 1} = N ={0,. . .,? 1}N ? 2.
? 2
0
/(l) /([) l [
= ~
/(l) /([)
/(l)[/([) = 8>>>
>>><
>>>>
>>
:
/(l) [ =l~, /([) l =[~,
/(l0. . .l= 1) [= <l= =,
/(l)[/([)
l =l0. . .l= [ =[0. . .[< = < = <<
l8 <[8 0 8 min{=,<}
l [ [ =l~
~ /([) ✓ /(l) /(l) = /(l) [/([)
[ l
= =< = 1
= l =[0. . .[= 1l= [=l0. . .l= 1[=
/([0. . .[= 1)
/(l) /([) l [
= ~
8 /(l) /([)
8 =/(l)\/([) =8>>><
>>>
:
/([) l ✓[ [ =l~, /(l) [ ✓l l =[~,
;.
l =l0. . .l= [ =[0. . .[< = < = <<
l8 <[8 0 8 min{=,<}
l [ [ = l~ [
l l = [~ ~
/([) ✓ /(l) /(l) ✓ /([) /(l) \/([) /(l) /([)
l 2 {0,. . .,? 1}N
{0,. . .,? 1}N
⇥ C n {0,. . .,? 1}N ⇥
9: {0,. . .,? 1}N ! ⇥
9 n
9
⇥
{ 0, 1 }
N? = 2 9
÷N
{0, 1} ={0, 1}N.
= =2 /(l) /([)
/(00)[/(01) =/(0), /(00)[/(0010) =/(00),
/(10)[/(110) =/(10)[/(110), /(01)[/(10) =/(01)[/(10).
/(l)
! 4
? = 2 /(l) /([)
/(00)\/(01) =;,
/(00)\/(0010) =/(0010), /(10)\/(110) =;,
/(01)\/(10) =;.
l =01
/(01) =/(00)[/(1).
9: {0, 1}N !⇥ 9 9([):/([0. . .[<)! B(Õ1
8=02[8
38 , 1/3<)
9 / (l) ✓ {0, 1}N
< 2N l =l0. . .l<
9 (/(l)) = (’1
==0
2G=
3= :G8 =l8, 808 <
)
=B
’1 8=0
2l8
38 ; 1 3<
! .
G 2bZ? < > 0 9 1 B
’1 8=0
2G8
38 ; 1 3<
! !
=/ (l0. . .l<).
9 1 B ✓ bZ? / (G) ✓ {0, 1}N ⌘
9 1 1 = 9 / (G)
B 9 1 9 9 1
9 {0, 1}N ⇥
G 2 {0, 1}N
B(9(G); 1/3=) /(G),
{~ 2 C |3(G,~) < 1/3=} G 2 ⇤,~ 2 N |G~ 2 N . G =01110
B(9(G); 1/33) /(011), B(9(G); 1/35) /(01110).
B(9(G); 1/35) ✓ B(9(G); 1/33), /(01110) ✓ /(011).
{0,. . .,? 1}N ? 2
? bZ?
⌧ ⌧ ⇤
⌧ h⌧,⇤i
(0⇤1)⇤2 =0⇤(1⇤2) 0,1,2 2⌧
4 2⌧ 4⇤G =G⇤4 G 2⌧ G 2⌧ 002⌧ 0⇤00=00⇤0=4
⌧
⌧
? 2N
N[?] = G0?0· · · +G8?8 |8 2N G8 2{0,. . .,? 1} ,
= (’<
8=0
G8%8 |G8 2{0,. . .,? 1} )
.
3? N[?]
3?(G,~) =3?(00+ · · · +0=?=,10+ · · · +1<?<) = |0: 1:|
?: ,
: 0: < 1: N[?] 3?
? b Z? =
(’1
8=0
G8%8 |G8 2 {0,. . .,? 1} )
.
0 = 00. . .0< {0,. . .,? 1} <
⌘(0)=Õ1
8=008?8
⌘ / (l) ✓ {0,. . .,? 1}N
< 2N l =l0. . .l<
⌘(/(l)) = (’1
==0
G=%= :G8 =l8, 808 <
)
=B
’1 8=0
l8?8; 1
?<
! .
G 2bZ? < > 0
⌘ 1 B
’1 8=0
G8%8; 1
?<
! !
=/ (l0. . .l<).
⌘ 1 B ✓ bZ? / (G) ✓ {0,. . .,? 1}N
⌘ ⌘ 1 1 / (G)
B ⌘ 1 ⌘ ⌘ 1
⌘ {0,. . .,? 1}N bZ?
i
? 2N @ 2N i@: {0,. . .,? 1}N ! {0,. . .,? 1}N
4 2bZ?
0,1, 0, 1 2bZ? 0+1 =2
= 2N 0 1
20 =(G+~)0 =G0+~0+Y0 mod ? Y0=0, ...
2= =(G+~)= =G=+~=+Y= mod? Y= =
( 0 G= 1+~= 1+Y= 1 < ?, 1 G= 1+~= 1+Y= 1 =?.
G 2bZ? G G G 2bZ?
G+ ( G) =0.
@ 2 N ? 2 N
q@: bZ? ! bZ? q@(G) =G +@ q@1(G) =G @ G 2bZ?
q = 2N q
q@= =q@ . . . q@
| {z }
=
=q=? =? =?+ · · · +?
| {z }
=
.
q bZ?
q bZ? q
@ 2N ? 2N i@: {0,. . .,? 1}N !
{0,. . .,? 1}N G 2 {0,. . .,? 1}N i
i@ (G) =⌘ 1(q@(⌘(G))).
⌘ :{0,. . .,? 1}N !bZ? q@:bZ? !bZ? @
-,.,/ 5 :- !. 6:. !/
5 6 6 5: - !/
* ✓ / / (6 5) 1(*) = {8G 2- |6(5(G)) 2*} = 8G 2- |G 2 5 1(6 1(*)) = 5 1(6 1(*)) 6 5 6 1(*)
. 5 1(6 1(*)) - (6 5)
5 6
(6 5) (6 5)
(6 5) 1
i@ {0,. . .,? 1}N
⇥ {0,. . .,? 1}N {0,. . .,? 1}N
bZ? bZ?
i@
⌘ ⌘ 1
q@
' '
i = ⌘ 1q⌘ ⌘
i
@=1 ? =2
q1:bZ2!bZ2 q1(G) =G+1 q11(G) =G 1 G 2bZ2 1, 12bZ2 : 2N
1=1+0·21+0·22+ · · ·=1+
’1
==1
0·?= 1=1+1·21+1·22+ · · · =
’1
==0
1·?=. q=(G)
@< 1
G G 2 bZ2
{0, 1}N
G =1+21+22+23+ · · ·= (111111111111. . .), G =1+0+0+0+0+ · · ·= (100000000000. . .), G+ ( G) =0+0+0+0+0+ · · ·= (000000000000. . .).
02bZ2 0=0+0·21+0·22+. . .
i2 q@2
{0, 1}N {0, 1}N {0, 1}N
b
Z2 bZ2 bZ2
i
i2
i
⌘
q1
q12
⌘
q1
⌘
'
0+0=0 0+1=1 1+1=0 1
G G
? =2 @ =1 / (l) ✓ {0, 1}N i
l =l8l0=l0. . .l< l8
l0 l8
i(l8l0) =
( 1l0 l8 1 =0,
0i(l0) l8 1 =1 08 =.
i
? = 2 @ = 1 / (G) ✓ {0, 1}N
<
l =l0. . .l< =l0l1l0.
l =l0+l1·21+l2·22+ · · · +l<·2<, 1=1+0·21+0·22+ · · · +0·2<.
l0+1 l1+0+n
n l0 = 1
0 = 2 mod 2 1 =21
l1+0+21 1 mod 2 1 2bZ2
0 02bZ2
i i(l0l1l0) = 0l1l0 l0 = 1
i(l1l0) 1 = 21
i(l0l1l0) = 1l1l0 l0 = 0
l G,~ 2 {0, 1}N
G =G0G0=G0G1G00 ~ =~0~0=~0G1~00 G0,~0 G00,~00
i 1 l =01 i 1
12bZ2 1=1000. . . {0, 1}N
i 1(/(l)) = G 2{0, 1}N |i(G)=l~ .
i 1 G =1G0 i(1G0) =0i(G0) =0~0 i 1 G =10G00 i(10G00) =0i (0G00) =01i(G00) =01~00
i(/(01)) = G 2{0, 1}N |i(G)=01~ , i(/(01)) =/(10).
( ⇥, ) )
i = 2 Z
⇥
G 2⇥ i
i
i: ⇥ !⇥
G 2⇥ G
G
i = 2Z
G ⇥
⇥
i
G
(⇥,)) ⇥
) :⇥ !⇥
(⇥,)) G 2 ⇥
⇥
{)=(G) |= 2Z}.
) G
G
(⇥,)) G 2 ⇥
= <0 )=(G) =G
(⇥,)) G 2⇥
~ 2⇥ n > 0 = 2Z
3()=(G),~) <n.
G
.
n )=(G)
Tnx
(⇥,)) )
n
G ~
G ⇥
(⇥,)) ) : ⇥ ! ⇥
i ?
@
?,@ 2 N G,~ 2 ⇥ i: ⇥ ! ⇥
? @ gcd(?,@) =1
i = 2N 3(i(G),~) < 1/3=
= G ~
⇧: bZ? ! Z/?=Z Õ1
<=00<?< ! Õ= 1
<=00<?<
mod (2=) ⇧
?=
bZ? Z/?=Z
G 2 Z? iG =G +@ ⇧(G +@)
(⇥,))
G 2bZ? Z/?=Z
bZ? Z/?=Z
⇧
i i
⇧
⇧(G) i(⇧(G)) = ⇧(G) +@ i b
Z? i
i
i bZ? gcd(?,@) = 1
gcd(?,@) =1
? =2 @ =3 gcd(?,@) =1
G 2 {0, 1}N G < =3 G =100G0
G i=: {0, 1}N +!3 {0, 1}N = 2Z
: 100 +!3 001 +!3 111 +!3 010 +!3 101 +!3 000 +!3 110 +!3 011 +!3 100.
3 0 1
8 i8(100) = 100
G
0 1 i=(G) <G = 2 N
==0 G
0 1 i n
i=(G) ~ 2{0, 1}N :
=
? =2 @ =2 gcd(?,@) =2 : 100 +!2 110 +!2 101 +!2 111 +!2 100,
: 010 +!2 001 +!2 011 +!2 000 +!2 010.
2 0 1
8
G
n G
: i=(G) ~
=
⇥,)
( + , ⇢ )
(⇠,))
G 2C
+1
+2
+3
+4
⇢1
⇢2
⇢3
= 1 (+,⇢)
+ +0. . .+=. . .
+0 = {E0} +1 = {E1,. . .,}
⇢ ⇢0. . .⇢=. . .
⇢0 = {40,. . .,} ⇢1 = {41,. . .,}
B: ⇢= ! += 1 B 1({E}) E [= 0+= A: ⇢= ! +=
A 1({E}) E [= 1+=
E0
(+,⇢) 0 < < =
+< += %<,=
%<,= ={(?<+1,?<+2,. . .,?=) |?8 2⇢8,< <8 =, A (?8) =B (?8+1),< < 8 <=}.
(⇥,))
+0 ={E0} ?
%⇢ ={(?1,?2,. . .) |?: 2⇢:, A (?:) =B(?:+1),: 1}.
?:
?:+1
= 2N (⇢,+) = |E=|=:
= "= 2":⇥: (N)
"=(8,9)= ⇢= 8 2+= 1 9 2+=
"= ="< =,< 2N
"= ="⇢
"⇢ "⇢ = 2 N
"⇢= ="⇢· · · · ·"⇢
| {z }
=
"⇢
"⇢ = (2),
| {z } "⇢ = 1 1 1 1
! ,
| {z }
"⇢ = 1 0 0 1
! .
| {z }
"⇢ (1)
%⇢
40. . .4= E0
l =40. . .4=
/ (l) ={lG 2%⇢ |l =40. . .4=,G 2%⇢},
={ l}.
%⇢
%⇢
(+,⇢, ) (+,⇢)
⇢ 4,40 2 ⇢ A(4) = A(40)
W = 41. . .4= d = 51. . .5= A(W) = A(d) (+,⇢, )
-<0G =U0U1. . . U 2⇢<0G -<8= =V0V1. . . V 2⇢<8=
(+,⇢, )
%⇢ ): %⇢ !%⇢
)(-<0G) =)(-<8=) )(G) =~(G=+1)G=+1 G= 2⇢8
G: 8 ⇢<0G : )(G) = (~1~2. . .~: 1(4: +
1)4:+1. . .) 4: +1 5
4: +1
G 2 {0, 1}N G = 1110011G0 G0
) G
)(G)=)(1110011G0) =000(0+1) 011G0=0001011G0.
: = 4 4: 8 ⇢<0G @ = 1 ? =2
{0, 1}N i1 G
i1(1110011) =0i1(110011) =00i1(10011) =· · ·=0001011.
{0, 1}N
(⇥,))
Emax Emin
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0
0 1
0 1
0 1
0
0
0 0
1
1
1
NTNU Norwegian University of Science and Technology Faculty of Information Technology and Electrical Engineering Department of Mathematical Sciences
Cantor Minimal Systems
Bachelor’s project in Mathematical Sciences Supervisor: Eduardo Ortega Esparza
May 2021