Difference between revisions of "ApCoCoA-1:Torus Knot Group"

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=== <div id="Torus Knot Group">[[:ApCoCoA:Symbolic data#Torus Knot Group|Torus Knot Group]]</div> ===
 
=== <div id="Torus Knot Group">[[:ApCoCoA:Symbolic data#Torus Knot Group|Torus Knot Group]]</div> ===
 
==== Description ====
 
==== Description ====
The Torus Knot Group
+
The Torus Knot Group is described by a space curve r(phi).
And has the following presentation:
+
                (cos(q*phi)+2)*cos(p*phi)
 +
With r(phi) = ( (cos(q*phi)+2)*sin(p*phi) ) 0<=phi<=2pi
 +
                        sin(q*phi)
 +
And has the following presentation with p and q is relatively prime:
 
  tng(a,b)= < a,b| a^p = b^q = 1 >
 
  tng(a,b)= < a,b| a^p = b^q = 1 >
  

Revision as of 14:21, 17 July 2014

Description

The Torus Knot Group is described by a space curve r(phi).

                (cos(q*phi)+2)*cos(p*phi) 
With r(phi) = ( (cos(q*phi)+2)*sin(p*phi) ) 0<=phi<=2pi
                        sin(q*phi)

And has the following presentation with p and q is relatively prime:

tng(a,b)= < a,b| a^p = b^q = 1 >

Reference

Michael Eisermann, Knotengruppen-Darstellungen und Invarianten von endlichem Typ, Rheinischen Friedrich-Wilhelms-Universität, Bonn, 2000

Computation

/*Use the ApCoCoA package ncpoly.*/

// Define the variable q,p of the Torusknotengroup
MEMORY.P := 2;
MEMORY.Q := 3;

Use ZZ/(2)[a,b,c,d];
NC.SetOrdering("LLEX");

Define CreateRelationsTorusknoten()
  Relations:=[];
  
  //add the inverse relations
  Append(Relations,[[a,c],[1]]);
  Append(Relations,[[c,a],[1]]);
  Append(Relations,[[b,d],[1]]);
  Append(Relations,[[d,b],[1]]);
  
  // add the relation a^p = b^q 
  Append(Relations,[[a^MEMORY.P],[b^MEMORY.Q]]);
   Return Relations;
EndDefine;

Relations:=CreateRelationsTorusknoten();
Relations;

Gb:=NC.GB(Relations,31,1,100,1000);
Gb;

Examples in Symbolic Data Format

 <FREEALGEBRA createdAt="2014-07-03" createdBy="strohmeier">
 	<vars>a,b,c,d</vars>
 	<uptoDeg>14</uptoDeg>
 	<basis>
 	<ncpoly>a*c-1</ncpoly>
 	<ncpoly>c*a-1</ncpoly>
 	<ncpoly>b*d-1</ncpoly>
 	<ncpoly>d*b-1</ncpoly>
 	<Comment>Relation: a^p=b^q</Comment>
 	<ncpoly>a*a-b*b*b</ncpoly> 
 	</basis>
 	<Comment>The partial LLex Gb has 198 elements</Comment>
 	<Comment>Torusknotengruppe_p2q3</Comment>
 	<Comment>Torusknotengruppe_p2q3 is isomorph to "Trefoil Knot Group"</Comment>
 </FREEALGEBRA>