The Jones Polynomial

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(For In[1] see Setup)

In[2]:= ?Jones
Jones[L][q] computes the Jones polynomial of a knot or link L as a function of the variable q.

In Naming and Enumeration we checked that the knots 6_1 and 9_46 have the same Alexander polynomial. Their Jones polynomials are different, though:

In[3]:= Jones[Knot[6, 1]][q]
Out[3]= -4 -3 -2 2 2 2 q - q q - - - q q q
In[4]:= Jones[Knot[9, 46]][q]
Out[4]= -6 -5 -4 2 -2 1 2 q - q q - -- q - - 3 q q
L8a6.gif
L8a6

On links with an even number of components the Jones polynomial is a function of , and hence it is often more convenient to view it as a function of , where :

In[5]:= Jones[Link[8, Alternating, 6]][q]
Out[5]= -(9/2) -(7/2) 3 3 4 3/2 -q q - ---- ---- - ------- 3 Sqrt[q] - 2 q 5/2 3/2 Sqrt[q] q q 5/2 7/2 2 q - q
In[6]:= PowerExpand[Jones[Link[8, Alternating, 6]][t^2]]
Out[6]= -9 -7 3 3 4 3 5 7 -t t - -- -- - - 3 t - 2 t 2 t - t 5 3 t t t

The Jones polynomial attains