Naming and Enumeration: Difference between revisions

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<tt><font color=blue>In[4]:=</font></tt><code><font color=red> Alexander[Knot[6, 1]][t]</font></code>
<tt><font color=blue>In[4]:=</font></tt><code><font color=red> Alexander[Knot[6, 1]][t]</font></code>


<tt>Out[4]=</tt> <math>-2 t+5-\frac{2}{t}</math>
<tt><font color=blue>Out[4]=</font></tt> <math>-2 t+5-\frac{2}{t}</math>
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<tt><font color=blue>In[5]:=</font></tt><code><font color=red> Alexander[Knot[9, 46]][t]</font></code>
<tt><font color=blue>In[5]:=</font></tt><code><font color=red> Alexander[Knot[9, 46]][t]</font></code>


<tt>Out[5]=</tt> <math>-2 t+5-\frac{2}{t}</math>
<tt><font color=blue>Out[5]=</font></tt> <math>-2 t+5-\frac{2}{t}</math>
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<tt><font color=blue>In[6]:=</font></tt><code><font color=red> Length[Skeleton[Link[6, Alternating, 4]]]</font></code>
<tt><font color=blue>In[6]:=</font></tt><code><font color=red> Length[Skeleton[Link[6, Alternating, 4]]]</font></code>


<tt>Out[6]=</tt> <math>3</math>
<tt><font color=blue>Out[6]=</font></tt> <math>3</math>
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<tt><font color=blue>In[9]:=</font></tt><code><font color=red> Length /@ {AllKnots[], AllLinks[]}</font></code>
<tt><font color=blue>In[9]:=</font></tt><code><font color=red> Length /@ {AllKnots[], AllLinks[]}</font></code>


<tt>Out[9]=</tt> <math>\{802,1424\}</math>
<tt><font color=blue>Out[9]=</font></tt> <math>\{802,1424\}</math>
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<!--$$Show[DrawPD[Knot[13, NonAlternating, 5016], {Gap -> 0.025}]]$$-->
<!--$$Show[DrawPD[Knot[13, NonAlternating, 5016], {Gap -> 0.025}]]$$-->
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<tt><font color=blue>In[10]:=</font></tt><code><font color=red> DrawPD[Knot[13, NonAlternating, 5016], {Gap -> 0.025}]</font></code>

<tt><font color=blue>Out[10]=</font> -Graphics-</tt>
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Revision as of 16:16, 23 August 2005

KnotTheory` comes loaded with some knot tables; currently, the Rolfsen table of prime knots with up to 10 crossings [Rolfsen], the Hoste-Thistlethwaite tables of prime knots with up to 16 crossings and the Thistlethwaite table of prime links with up to 11 crossings (see Further Knot Theory Software#Knotscape):

(For In[1] see Setup)

In[2]:= ?Knot

Knot[n, k] denotes the kth knot with n crossings in the Rolfsen table. Knot[11, Alternating, k] denotes the kth alternating 11-crossing knot in the Hoste-Thistlethwaite table. Knot[11, NonAlternating, k] denotes the kth non alternating 11-crossing knot in the Hoste-Thistlethwaite table.

In[3]:= ?Link

Link[n, Alternating, k] denotes the kth alternating n-crossing link in the Thistlethwaite table. Link[n, NonAlternating, k] denotes the kth non alternating n-crossing link in the Thistlethwaite table.

Thus, for example, let us verify that the knots 6_1 and 9_46 have the same Alexander polynomial:

In[4]:= Alexander[Knot[6, 1]][t]

Out[4]=


In[5]:= Alexander[Knot[9, 46]][t]

Out[5]=

We can also check that the Borromean rings, L6a4 in the Thistlethwaite table, is a 3-component link:

In[6]:= Length[Skeleton[Link[6, Alternating, 4]]]

Out[6]=

In[7]:= ?AllKnots

AllKnots[] return a list of all the named knots known to KnotTheory.m.

In[8]:= ?AllLinks

AllLinks[] return a list of all the named links known to KnotTheory.m.

Thus at the moment there are 802 knots and 1424 links known to KnotTheory`:

In[9]:= Length /@ {AllKnots[], AllLinks[]}

Out[9]=

In[10]:= DrawPD[Knot[13, NonAlternating, 5016], {Gap -> 0.025}]

Out[10]= -Graphics-

References

[Rolfsen] ^  D. Rolfsen, Knots and Links, Publish or Perish, Mathematics Lecture Series 7, Wilmington 1976.