"Rubberband" Brunnian Links: Difference between revisions

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(New page: {{Manual TOC Sidebar}} =="Rubberband" Brunnian Links== A "Rubberband" Brunnian link is obtained by connecting unknots in a closed chain as illustrated in the diagram of the 10-component l...)
 
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{{Manual TOC Sidebar}}
{{Manual TOC Sidebar}}


A "Rubberband" [[Brunnian link]] is obtained by connecting unknots in a closed chain as illustrated in the diagram of the 10-component link, where the last knot gets connected to the first one.
=="Rubberband" Brunnian Links==
A "Rubberband" Brunnian link is obtained by connecting unknots in a closed chain as illustrated in the diagram of the 10-component link, where the last knot gets connected to the first one.


{|
{|
Line 21: Line 20:
{{In|
{{In|
n = 1 |
n = 1 |
in = <nowiki>Subscript[K, 0] =
in = <nowiki>K0 =
PD[X[1, 10, 5, 12], X[2, 12, 6, 14], X[5, 11, 8, 13],
PD[X[1, 10, 5, 12], X[2, 12, 6, 14], X[5, 11, 8, 13],
X[6, 13, 9, 15], X[10, 0, 16, 4], X[11, 4, 17, 8], X[14, 7, 19, 3],
X[6, 13, 9, 15], X[10, 0, 16, 4], X[11, 4, 17, 8], X[14, 7, 19, 3],
Line 34: Line 33:
n = 2 |
n = 2 |
in = <nowiki>RubberBandBrunnian[n_] :=
in = <nowiki>RubberBandBrunnian[n_] :=
Join @@ Table[
Join @@ Table[K0 /. j_Integer :> j + 16 k, {k, 0, n - 1}] /. {16
Subscript[K, 0] /. j_Integer :> j + 16 k, {k, 0, n - 1}] /. {16
n -> 0, 16 n + 1 -> 1, 16 n + 2 -> 2, 16 n + 3 -> 3}</nowiki>}}
n -> 0, 16 n + 1 -> 1, 16 n + 2 -> 2, 16 n + 3 -> 3}</nowiki>}}
<!--END-->
<!--END-->
Line 41: Line 39:
For instance, let us draw the links with three, four, and five components and compute their Jones polynomials:
For instance, let us draw the links with three, four, and five components and compute their Jones polynomials:


<!--$$RBB3=RubberBandBrunnian[3];
<!--$$DrawMorseLink[RBB3=RubberBandBrunnian[3]]$$-->
RBB4=RubberBandBrunnian[4];
RBB5=RubberBandBrunnian[5];$$-->
<!--Robot Land, no human edits to "END"-->
<!--Robot Land, no human edits to "END"-->
{{In|
{{Graphics|
n = 3 |
n = 4 |
in = <nowiki>RBB3=RubberBandBrunnian[3];RBB4=RubberBandBrunnian[4];RBB5=RubberBandBrunnian[5];</nowiki>}}
in = <nowiki>DrawMorseLink[RBB3=RubberBandBrunnian[3]]</nowiki> |
img= Rubberband_Brunnian_Links_Out_3.gif |
out= <nowiki>-Graphics-</nowiki>}}
<!--END-->
<!--END-->


<!--$$Jones[RBB3][q]$$-->

<!--$$DrawMorseLink/@{RBB3,RBB4,RBB5}$$-->
<!--Robot Land, no human edits to "END"-->
<!--Robot Land, no human edits to "END"-->
{{InOut|
{{InOut|
n = 4 |
n = 5 |
in = <nowiki>DrawMorseLink/@{RBB3,RBB4,RBB5}</nowiki> |
in = <nowiki>Jones[RBB3][q]</nowiki> |
out= <nowiki> 2 3 4 5 7 8 9 10
out= <nowiki>{-Graphics-, -Graphics-, -Graphics-}</nowiki>}}
-q + 5 q - 11 q + 14 q - 10 q + 11 q - 18 q + 24 q - 18 q +
11 13 14 15 16 17
11 q - 10 q + 14 q - 11 q + 5 q - q</nowiki>}}
<!--END-->
<!--END-->


<!--$$DrawMorseLink[RBB4=RubberBandBrunnian[4]]$$-->
<!--$$RBJones= Jones[#][q] & /@ {RBB3, RBB4, RBB5}$$-->
<!--Robot Land, no human edits to "END"-->
{{Graphics|
n = 7 |
in = <nowiki>DrawMorseLink[RBB4=RubberBandBrunnian[4]]</nowiki> |
img= Rubberband_Brunnian_Links_Out_6.gif |
out= <nowiki>-Graphics-</nowiki>}}
<!--END-->

<!--$$Jones[RBB4][q]$$-->
<!--Robot Land, no human edits to "END"-->
<!--Robot Land, no human edits to "END"-->
{{InOut|
{{InOut|
n = 5 |
n = 8 |
in = <nowiki>RBJones= Jones[#][q] & /@ {RBB3, RBB4, RBB5}</nowiki> |
in = <nowiki>Jones[RBB4][q]</nowiki> |
out= <nowiki> 2 3 4 5 7 8 9 10
out= <nowiki> 3/2 5/2 7/2 9/2 11/2 13/2 15/2
{-q + 5 q - 11 q + 14 q - 10 q + 11 q - 18 q + 24 q - 18 q +
-q + 7 q - 24 q + 49 q - 56 q + 18 q + 51 q -
11 13 14 15 16 17
17/2 19/2 21/2 23/2 25/2 27/2
11 q - 10 q + 14 q - 11 q + 5 q - q ,
111 q + 131 q - 100 q + 32 q + 32 q - 100 q +
3/2 5/2 7/2 9/2 11/2 13/2 15/2
29/2 31/2 33/2 35/2 37/2 39/2
-q + 7 q - 24 q + 49 q - 56 q + 18 q + 51 q -
131 q - 111 q + 51 q + 18 q - 56 q + 49 q -
17/2 19/2 21/2 23/2 25/2
41/2 43/2 45/2
111 q + 131 q - 100 q + 32 q + 32 q -
24 q + 7 q - q</nowiki>}}
<!--END-->

27/2 29/2 31/2 33/2 35/2 37/2
<!--$$DrawMorseLink[RBB5=RubberBandBrunnian[5]]$$-->
100 q + 131 q - 111 q + 51 q + 18 q - 56 q +
<!--Robot Land, no human edits to "END"-->
{{Graphics|
39/2 41/2 43/2 45/2
n = 10 |
49 q - 24 q + 7 q - q ,
in = <nowiki>DrawMorseLink[RBB5=RubberBandBrunnian[5]]</nowiki> |
img= Rubberband_Brunnian_Links_Out_9.gif |
2 3 4 5 6 7 8 9
out= <nowiki>-Graphics-</nowiki>}}
-q + 9 q - 40 q + 110 q - 189 q + 167 q + 57 q - 414 q +
<!--END-->

<!--$$Jones[RBB5][q]$$-->
<!--Robot Land, no human edits to "END"-->
{{InOut|
n = 11 |
in = <nowiki>Jones[RBB5][q]</nowiki> |
out= <nowiki> 2 3 4 5 6 7 8 9
-q + 9 q - 40 q + 110 q - 189 q + 167 q + 57 q - 414 q +
10 11 12 13 14 15
10 11 12 13 14 15 16
660 q - 581 q + 189 q + 305 q - 672 q + 816 q -
660 q - 581 q + 189 q + 305 q - 672 q + 816 q - 672 q +
16 17 18 19 20 21 22
17 18 19 20 21 22 23
672 q + 305 q + 189 q - 581 q + 660 q - 414 q + 57 q +
305 q + 189 q - 581 q + 660 q - 414 q + 57 q + 167 q -
23 24 25 26 27 28
24 25 26 27 28
167 q - 189 q + 110 q - 40 q + 9 q - q }</nowiki>}}
189 q + 110 q - 40 q + 9 q - q</nowiki>}}
<!--END-->
<!--END-->


We can also check that when one component is removed the remaining link is trivial:
We can also check that when one component is removed the remaining link is trivial:

<!--$$Import["http://katlas.org/w/index.php?title=SubLink.m&action=raw"];$$-->
<!--Robot Land, no human edits to "END"-->
{{In|
n = 12 |
in = <nowiki>Import["http://katlas.org/w/index.php?title=SubLink.m&action=raw"];</nowiki>}}
<!--END-->


<!--$$S = SubLink[RubberBandBrunnian[5], {1, 2, 3, 4}];$$-->
<!--$$S = SubLink[RubberBandBrunnian[5], {1, 2, 3, 4}];$$-->
<!--Robot Land, no human edits to "END"-->
<!--Robot Land, no human edits to "END"-->
{{In|
{{In|
n = 6 |
n = 13 |
in = <nowiki>S = SubLink[RubberBandBrunnian[5], {1, 2, 3, 4}];</nowiki>}}
in = <nowiki>S = SubLink[RubberBandBrunnian[5], {1, 2, 3, 4}];</nowiki>}}
<!--END-->
<!--END-->
Line 107: Line 133:
<!--Robot Land, no human edits to "END"-->
<!--Robot Land, no human edits to "END"-->
{{InOut|
{{InOut|
n = 7 |
n = 14 |
in = <nowiki>J=Factor[Jones[S][q]]</nowiki> |
in = <nowiki>J=Factor[Jones[S][q]]</nowiki> |
out= <nowiki> 6 3
out= <nowiki> 6 3
Line 113: Line 139:
<!--END-->
<!--END-->



==Brunnian Braids==
Similarly, in the case of Brunnian braids, removing one strand gives us a trivial braid. We can verify that using the following two programs. The first one constructs a Brunnian braid while the second one removes a selected strand:
Similarly, in the case of Brunnian braids, removing one strand gives us a trivial braid. We can verify that using the following two programs. The first one constructs a Brunnian braid while the second one removes a selected strand:


Line 124: Line 150:
((b0 ** BR[n, {n - 1, n - 1}]) ** Inverse[b0]) **
((b0 ** BR[n, {n - 1, n - 1}]) ** Inverse[b0]) **
BR[n, {1 - n, 1 - n}]
BR[n, {1 - n, 1 - n}]
]$$--> <!--END-->
]$$-->
<!--Robot Land, no human edits to "END"-->
{{In|
n = 15 |
in = <nowiki>BR /: Inverse[BR[n_, l_List]] := BR[n, -Reverse[l]];
BR /: BR[n1_, l1_] ** BR[n2_, l2_] := BR[Max[n1, n2], Join[l1, l2]];
BrunnianBraid[2] = BR[2, {1, 1}];
BrunnianBraid[n_] /; n > 2 := Module[
{b0},
b0 = BrunnianBraid[n - 1];
((b0 ** BR[n, {n - 1, n - 1}]) ** Inverse[b0]) **
BR[n, {1 - n, 1 - n}]
]</nowiki>}}
<!--END-->


<!--$$DeleteStrand[k_, BR[n_, l_List]] := BR[n - 1, DeleteStrand[k, l]];
<!--$$DeleteStrand[k_, BR[n_, l_List]] := BR[n - 1, DeleteStrand[k, l]];
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k == Abs[j1] + 1, DeleteStrand[k - 1, {js}],
k == Abs[j1] + 1, DeleteStrand[k - 1, {js}],
k > Abs[j1] + 1, {j1}~Join~DeleteStrand[k, {js}]
k > Abs[j1] + 1, {j1}~Join~DeleteStrand[k, {js}]
]$$--> <!--END-->
]$$-->
<!--Robot Land, no human edits to "END"-->
{{In|
n = 16 |
in = <nowiki>DeleteStrand[k_, BR[n_, l_List]] := BR[n - 1, DeleteStrand[k, l]];
DeleteStrand[k_, {}] = {};
DeleteStrand[k_, {j1_, js___}] := Which[
k < Abs[j1], {j1 - Sign[j1]}~Join~DeleteStrand[k, {js}],
k == Abs[j1], DeleteStrand[k + 1, {js}],
k == Abs[j1] + 1, DeleteStrand[k - 1, {js}],
k > Abs[j1] + 1, {j1}~Join~DeleteStrand[k, {js}]
]</nowiki>}}
<!--END-->


Testing for the Brunnian braid with four strands, we get:
Testing for the Brunnian braid with four strands, we get:


<!--$$(b = BrunnianBraid[4]) // BraidPlot $$--> <!--END-->
<!--$$(b = BrunnianBraid[4]) // BraidPlot $$-->
<!--Robot Land, no human edits to "END"-->
{{Graphics|
n = 18 |
in = <nowiki>(b = BrunnianBraid[4]) // BraidPlot </nowiki> |
img= Rubberband_Brunnian_Links_Out_17.gif |
out= <nowiki>-Graphics-</nowiki>}}
<!--END-->


<!--$$Jones[b][q]$$--> <!--END-->
<!--$$Jones[b][q]$$-->
<!--Robot Land, no human edits to "END"-->
{{InOut|
n = 19 |
in = <nowiki>Jones[b][q]</nowiki> |
out= <nowiki> -(11/2) 4 6 5 5 1 3/2
-q + ---- - ---- + ---- - ---- - ------- - Sqrt[q] - 5 q +
9/2 7/2 5/2 3/2 Sqrt[q]
q q q q
5/2 7/2 9/2 11/2
5 q - 6 q + 4 q - q</nowiki>}}
<!--END-->


<!--$$(bb = DeleteStrand[4, b]) // BraidPlot$$--> <!--END-->
<!--$$(bb = DeleteStrand[4, b]) // BraidPlot$$-->
<!--Robot Land, no human edits to "END"-->
{{Graphics|
n = 21 |
in = <nowiki>(bb = DeleteStrand[4, b]) // BraidPlot</nowiki> |
img= Rubberband_Brunnian_Links_Out_20.gif |
out= <nowiki>-Graphics-</nowiki>}}
<!--END-->


<!--$$Jones[#][q] & /@ {bb, BR[3, {}]}$$--> <!--END-->
<!--$$Jones[#][q] & /@ {bb, BR[3, {}]}$$-->
<!--Robot Land, no human edits to "END"-->
{{InOut|
n = 22 |
in = <nowiki>Jones[#][q] & /@ {bb, BR[3, {}]}</nowiki> |
out= <nowiki> 1 1
{2 + - + q, 2 + - + q}
q q</nowiki>}}
<!--END-->

Latest revision as of 14:03, 20 October 2013


KnotTheory`/Navigation 

The Mathematica Package KnotTheory`

A "Rubberband" Brunnian link is obtained by connecting unknots in a closed chain as illustrated in the diagram of the 10-component link, where the last knot gets connected to the first one.

The Rubberband link with 10 components Brunnian Link Example.PNG

If we number the strands in one section of the link as shown and proceed with numbering each following section in the same manner, we can get its PD form. The PD of any "Rubberband" link can be generated in this way by varying the desired number of components:

(For In[1] see Setup)

In[1]:= K0 = PD[X[1, 10, 5, 12], X[2, 12, 6, 14], X[5, 11, 8, 13], X[6, 13, 9, 15], X[10, 0, 16, 4], X[11, 4, 17, 8], X[14, 7, 19, 3], X[15, 9, 18, 7]];
In[2]:= RubberBandBrunnian[n_] := Join @@ Table[K0 /. j_Integer :> j + 16 k, {k, 0, n - 1}] /. {16 n -> 0, 16 n + 1 -> 1, 16 n + 2 -> 2, 16 n + 3 -> 3}

For instance, let us draw the links with three, four, and five components and compute their Jones polynomials:

In[4]:= DrawMorseLink[RBB3=RubberBandBrunnian[3]]
Rubberband Brunnian Links Out 3.gif
Out[4]= -Graphics-
In[5]:= Jones[RBB3][q]
Out[5]= 2 3 4 5 7 8 9 10 -q + 5 q - 11 q + 14 q - 10 q + 11 q - 18 q + 24 q - 18 q + 11 13 14 15 16 17 11 q - 10 q + 14 q - 11 q + 5 q - q
In[7]:= DrawMorseLink[RBB4=RubberBandBrunnian[4]]
Rubberband Brunnian Links Out 6.gif
Out[7]= -Graphics-
In[8]:= Jones[RBB4][q]
Out[8]= 3/2 5/2 7/2 9/2 11/2 13/2 15/2 -q + 7 q - 24 q + 49 q - 56 q + 18 q + 51 q - 17/2 19/2 21/2 23/2 25/2 27/2 111 q + 131 q - 100 q + 32 q + 32 q - 100 q + 29/2 31/2 33/2 35/2 37/2 39/2 131 q - 111 q + 51 q + 18 q - 56 q + 49 q - 41/2 43/2 45/2 24 q + 7 q - q
In[10]:= DrawMorseLink[RBB5=RubberBandBrunnian[5]]
Rubberband Brunnian Links Out 9.gif
Out[10]= -Graphics-
In[11]:= Jones[RBB5][q]
Out[11]= 2 3 4 5 6 7 8 9 -q + 9 q - 40 q + 110 q - 189 q + 167 q + 57 q - 414 q + 10 11 12 13 14 15 16 660 q - 581 q + 189 q + 305 q - 672 q + 816 q - 672 q + 17 18 19 20 21 22 23 305 q + 189 q - 581 q + 660 q - 414 q + 57 q + 167 q - 24 25 26 27 28 189 q + 110 q - 40 q + 9 q - q

We can also check that when one component is removed the remaining link is trivial:

In[12]:= Import["http://katlas.org/w/index.php?title=SubLink.m&action=raw"];
In[13]:= S = SubLink[RubberBandBrunnian[5], {1, 2, 3, 4}];
In[14]:= J=Factor[Jones[S][q]]
Out[14]= 6 3 -(q (1 + q) )


Similarly, in the case of Brunnian braids, removing one strand gives us a trivial braid. We can verify that using the following two programs. The first one constructs a Brunnian braid while the second one removes a selected strand:

In[15]:= BR /: Inverse[BR[n_, l_List]] := BR[n, -Reverse[l]]; BR /: BR[n1_, l1_] ** BR[n2_, l2_] := BR[Max[n1, n2], Join[l1, l2]]; BrunnianBraid[2] = BR[2, {1, 1}]; BrunnianBraid[n_] /; n > 2 := Module[ {b0}, b0 = BrunnianBraid[n - 1]; ((b0 ** BR[n, {n - 1, n - 1}]) ** Inverse[b0]) ** BR[n, {1 - n, 1 - n}] ]
In[16]:= DeleteStrand[k_, BR[n_, l_List]] := BR[n - 1, DeleteStrand[k, l]]; DeleteStrand[k_, {}] = {}; DeleteStrand[k_, {j1_, js___}] := Which[ k < Abs[j1], {j1 - Sign[j1]}~Join~DeleteStrand[k, {js}], k == Abs[j1], DeleteStrand[k + 1, {js}], k == Abs[j1] + 1, DeleteStrand[k - 1, {js}], k > Abs[j1] + 1, {j1}~Join~DeleteStrand[k, {js}] ]

Testing for the Brunnian braid with four strands, we get:

In[18]:= (b = BrunnianBraid[4]) // BraidPlot
Rubberband Brunnian Links Out 17.gif
Out[18]= -Graphics-
In[19]:= Jones[b][q]
Out[19]= -(11/2) 4 6 5 5 1 3/2 -q + ---- - ---- + ---- - ---- - ------- - Sqrt[q] - 5 q + 9/2 7/2 5/2 3/2 Sqrt[q] q q q q 5/2 7/2 9/2 11/2 5 q - 6 q + 4 q - q
In[21]:= (bb = DeleteStrand[4, b]) // BraidPlot
Rubberband Brunnian Links Out 20.gif
Out[21]= -Graphics-
In[22]:= Jones[#][q] & /@ {bb, BR[3, {}]}
Out[22]= 1 1 {2 + - + q, 2 + - + q} q q
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