Dr David McGrath

Dr David McGrath

Dr David McGrath

Spine Physician

MB BS (Hons) FAFOM, RACP, FAFMM
Master of Pain Medicine


The vertex semigroup structure is a 4semigroup (one of 126 possibilities) 

NxN =4^4^2 =4^16. Under B2(Y)=2^4=16 (Rectangular Band)
 LR Ideals

1=xyx

L

2=xyz

L

3=zyx

L

4=zyz

L

1=xyx R 1 2 1 2
2=xyz R 1 2 1 2
3=zyx R 3 4 3 4
4=zyz R 3 4 3 4

1.Idempotent aa=a

2.Associative (ab)c=a(bc)

3.Rectangular abc=ac.  aba=a   (aa =a) (point1)

Greens Relation L/R Class
   1 2 3 4
 L  1133 2244 1133 2244
 R  1212 1212 3434 3434
 J

xxxx

yyyy

yyyy

xxxx

L,R Classes L={ (13), (24) } and R={ (12), (34) }

(1L3, 2L4) and (1R2, 3R4)   

J Classes  J={ (14) , (23) } 

SaS=SbS

H  Classes

aLb=aRb  eg 1L2=1R2   ie not possible no H class, except trivial aLa=aRa

D Class D={ (14), (23) }

(1R2,2L4) and/or (4R3 ,3L1) implies (1,4) belong same D class.

(3R4,4L2) and/or  (2R1,1L3) implies (2,3) belong same D class.

 

(16=2^4) Transformation (Semigroup/Monoid under Function Composition)            with 5 subgroups/1 subsemigroup (+further subsemigroups ) 
R Classes  11 22  
33


L Class

(f) 1133 ff=f(2)

 

D Class

(g) 2233 ff=f(2)

 (a) Z2

1233* ff=f (1)

(2133) fff=f (3)

44

 

D Class

(h) 1144 ff=f(2)

 

L Class

(e) 2244 ff=f (2)

 (b) Z2

1244* ff=f (1)

(2144) fff=f(3)

 

(c) Z2

1134* ff=f(1)

(1143) fff=f(3)

(d) Z2

2234* ff=f(1)

(2243)fff=f(3)

(i) Klein 4-Group

(2134) fff=f(2)      (2143) fff=f(4)

1234* ff=f(0)   (1243) fff=f(2)

 (brackets)=number of category changes and generative set.  ff..=cycle length

Generative Set
Set  fff=f 2134 2143 1243 1143 2243 2133 2144
Inverses 2134 2143 1243 - - - -
Single Permutation Set  ff=f     1234 1134  2234  1244  1233 

A generative set can be identified. Each Z2 group has one generative permutation (1143,2243,2133,2144).

The K4 group has 3 (2134,2143,1243) (all produce the identity). All others can be derived. The generative set are all 3power idempotent. 

Four Combinations of (a,b,c,d)=(ac,ad,bc,bd) (=16x4=64)

(b,d) Matrix (not closed)

 bd   1244 (2144) 2234 (2243)
           
1244   1244
(2144) 2244 2233
(2144)   (2144) 1244 2244 2233
2234   2244 1144 2234 (2243)
(2243)   2444 1144 (2243) 2234

 Non Closed structure with 2 -Z2 subgroups (1244,2144) (2234, 2243)

(b,c) Matrix (not closed)
bc   1244 (2144) 1134 (1143)
           
1244   1244 (2144) 1144 1133
(2144)   (2144) 1244 1144 1133
1134   1144 2244 1134 (1143)
(1143)   1144 2244 (1143) 1134

 

Klein 4-Group (i=1234,aa=i,ab=ba)

 ii   #1234 #2143 1243 2134
           
#1234   #1234 #2143 1243 2134
#2143   #2143 #1234 2134 1243
1243   1243 2134 #1234 #2143
2134   2134 1243 #2143 #1234

4-Group Z2xZ2 Klein 4-Group with three subgroups (#1234,#2143) (1234,1243) (1234,2134) 

 

(K4,b) Matrix (not closed)
 ib   1234 (2143) (1243) (2134) 1244 (2144)
             L  L
1234   1234 2143 1243 2134 1244 (2144)
2143   2143 1234 2134 1243 (2144) 1244
1243   1243 2134 1234 2143 1244 (2144)
2134   2134 1243 2143 1243 (2144) 1244
1244  R 1244 (2133) 1233 (2144) 1244 (2144)
(2144)  R (2144) 1233 (2133) 1244 (2144) 1244

 

(K4,e) Matrix (not closed)
 ie   1234
(2143) (1243) (2134) 2244
             L
1234   1234 2143 1243 2134 2244 
(2143)   2143 1234 2134 1243 2244 
(1243)   1243 2134 1234 2143 2244 
(2134)   2134 1243 2143 1243 2244 
2244  R 2244  1133  2233  1144  2244 

 

(e,f,g,h) Idempotent 4-Semigroup and (b) Z2 group

    1144 2233 1133 2244   1244 (2144)
               L
1144   1144 2233 1133 2244   1144  2244 
2233   1144 2233 1133 2244   2244  1144 
1133   1144 2233 1133 2244   1144  2244 
2244   1144 2233 1133 2244   2244  1144 
                 
1244 R 1144  2233  1133  2244    1244  (2144) 
(2144) 1144  2233  1133  2244    (2144)  1244 

Idempotent 4-Semigroup with (2) 2-subsemigroups (1133,2244) and (1144,2233)

(c,d)  4-Semigroup

 cd   2234 2243 1134 1143
           
2234   2234 2243 1134 1143
2243   2243 2234 1143 1134
1134   2234 2243 1134 1143
1143   2243 2234 1143 1134

4-Semigroup with 2 Z2 groups (1134,1143) and (2234,2243)

 

Closed under Binary Function composition.  (fg) belongs set of 16 functions.  

Transformation Semigroup is a pair (N,S)  N=(1,3,2,4) and S=(16 functions, closed under composition)

Not the full transformation semigroup, S4xS4=256 functions (n^n) 

 

Only (0,1) functions supported by B2(Y). ie (1234), (1134), (1233),(2234),(1244).

 

 

 

 



©Copyright 2007 Dr David McGrath. All rights reserved