Dr David McGrath

Dr David McGrath

Dr David McGrath

Spine Physician

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


 All elements of K4 belong to their own conjugacy class.  eg (HRH=R, VRV=R, IRI=R) The four classes are I,H,R,V

Abelian implies aG=Ga all elements (a) of a subgroup. Thus LEFT coset=RIGHT coset. All subgroups are NORMAL.

HH=VV=RR=I.  ie permutations are OWN inverse.

HR=V, RV=H, HV=R

G/H=(R,V)  G/R=(H,V)  G/V=(R,H)  Quotient Groups.

Thus two subgroups sufficient to describe the actions of the group.  eg R,H

 

Replace (xz) by generic (&%).  Replace 1,2,3,4 by non ordered (a,b,c,d)

Four sets:

(a=1,b=2,c=3,d=4,&=x,%=z)

(a=2,b=1,c=4,d=3,&=x,%=z)

(a=3,b=4,c=1,d=2,&=z,%=x)

(a=4,b=3,c=2,d=1,&=z,%=x)

Generic Neighbourhood Object (a)
  Creation  b&a=a   Creation  b%c=a  

Participation  c&a=c

      Recursion  a%c=a
    (a)Neighbourhood     
Participation  d&a=c       Recursion  a&a=a
  Destruction  a&b=b   Destruction  a%d=b  

 

1.(b) creates and destroys (a)  eg  for (1)   [1@ 2=2, 1@4=2 ] and [2@1=1, 2 @ 3 =1]

2.(a),(c) recursion modification eg for (1) [1@3=1] and [1@1=1] 

3. (a)(d) mutual partners in creating (b)(c) [3@1=3] and [4@1=3]

4. Participation/Recursion preserves total (a)

5. Total (a)+(b) constant. Extreme imbalance implies (a)=0 and no participation in (c) recursion/creation.

 

Group Matrix on Neighbourhood Set
  N1 N2 N3 N4
N1 1 2 3 4
N2 2 1 4 3
N3 3 4 1 2
N4 4 3 2 1

 

Z2 (H) LEFT Action on Neighbourhood Set

  N1 N2 N3 N4
Identity (1234) 1234 2143 3412 4321
Horizontal Reflection=H(12)(34)=2143 2143 1234 4321 3412

 ie (12)(34) LEFT Cosets under H Reflection

 

Z2 (H) RIGHT Coset Action
  Identity 2143
N1  1234 2143 
N2  2143 1234 
N3  3412 4321 
N4  4312 3412 

 ie (12)(34) RIGHT Cosets under H Reflection.  RIGHT=LEFT  ie H is Normal Subgroup

 

Z2(V) Subgroup LEFT Action on Neighbourhood Set

  N1 N2 N3  N4 
Identity I=(1234) 1234 2143  3412  4312 
Vertical Reflection=V(13)(24)=3412  3412 4321  1234  2143 

ie (13)(24) Orbits under V Reflection 

 

Z2(V) RIGHT Coset Action
  Identity 1234 3412
N1 1234 3412
N2 2143 4321
N3 3412 1234
N4 4312 2143

 

Z2(R) Subgroup LEFT Action on Neighbourhood Set

  N1 N2 N3 N4
Identity I=(1234) 1234 2143 3412 4312
Rotation =R(14)(23)=4321                      4321 3412 2143 1234

ie (14)(23) Orbits under R Rotation 

 

 

 

 

 

K4 (Z2xZ2) Group Transitive Action on Neighbourhood Set

  N1 N2 N3 N4
Identity=I(1234) xyx  xyz zyx zyz 
Horizontal Reflection=H(12)(34)  xy(x)z  xy(x)x  zy(z)z  zy(z)x 
Vertical Reflection=V(13)(24)  zy(z)x  zy(z)z  xy(x)x  xy(x)z 
Rotation=R(14)(23)  zy(z)z  zy(z)x  xy(x)z  xy(x)x 
HH=I  xy(xx)x xy(zz)z  zy(zz)x  zy(zz)z 
VV=I  xy(zz)x  xy(zz)z  zy(xx)x  zy(xx)z 
RR=I  xyx  xyz  zyx  zyz 
HV=R  zy(xz)z  zy(xz)x  xy(zx)z  xy(zx)x 
VH=R zy(zx)z zy(zx)x xy(xz)z xy(xz)x
HR=V zy( )x      
RH=V        

 

 

 

 



©Copyright 2007 Dr David McGrath. All rights reserved