© | Dror Bar-Natan: The Knot Atlas: The Rolfsen Knot Table:
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77
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    8.1
KnotPlot
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   The Alternating Knot 81   

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Acknowledgement

8.1
KnotPlot

PD Presentation: X1425 X9,12,10,13 X3,11,4,10 X11,3,12,2 X5,16,6,1 X7,14,8,15 X13,8,14,9 X15,6,16,7

Gauss Code: {-1, 4, -3, 1, -5, 8, -6, 7, -2, 3, -4, 2, -7, 6, -8, 5}

DT (Dowker-Thistlethwaite) Code: 4 10 16 14 12 2 8 6

Minimum Braid Representative:


Length is 10, width is 5
Braid index is 5

A Morse Link Presentation:

3D Invariants:
Symmetry Type Unknotting Number 3-Genus Bridge/Super Bridge Index Nakanishi Index
Reversible 1 1 2 / 4--5 1

Alexander Polynomial: - 3t-1 + 7 - 3t

Conway Polynomial: 1 - 3z2

Other knots with the same Alexander/Conway Polynomial: {...}

Determinant and Signature: {13, 0}

Jones Polynomial: q-6 - q-5 + q-4 - 2q-3 + 2q-2 - 2q-1 + 2 - q + q2

Other knots (up to mirrors) with the same Jones Polynomial: {K11n70, ...}

A2 (sl(3)) Invariant: q-20 + q-18 - q-12 - q-10 + q2 + q6 + q8

HOMFLY-PT Polynomial: a-2 - z2 - a2z2 - a4 - a4z2 + a6

Kauffman Polynomial: - a-2 + a-2z2 + a-1z3 + z4 - az3 + az5 - 2a2z4 + a2z6 - 3a3z + 5a3z3 - 4a3z5 + a3z7 - a4 + 7a4z2 - 8a4z4 + 2a4z6 - 3a5z + 7a5z3 - 5a5z5 + a5z7 - a6 + 6a6z2 - 5a6z4 + a6z6

V2 and V3, the type 2 and 3 Vassiliev invariants: {-3, 3}

Khovanov Homology:
(The squares with yellow highlighting are those on the "critical diagonals", where j-2r=s+1 or j-2r=s+1, where s=0 is the signature of 81. Nonzero entries off the critical diagonals (if any exist) are highlighted in red.)
  
trqj r = -6r = -5r = -4r = -3r = -2r = -1r = 0r = 1r = 2
j = 5        1
j = 3         
j = 1      21 
j = -1     11  
j = -3    11   
j = -5   11    
j = -7   1     
j = -9 11      
j = -11         
j = -131        

 n  Coloured Jones Polynomial (in the (n+1)-dimensional representation of sl(2))
2 q-18 - q-17 - q-16 + 2q-15 - q-14 - 2q-13 + 3q-12 - 3q-10 + 3q-9 - 3q-7 + 3q-6 + q-5 - 3q-4 + 2q-3 + q-2 - 3q-1 + 2 - 2q2 + 2q3 - q5 + q6
3 q-36 - q-35 - q-34 + 2q-32 - 2q-30 - q-29 + 3q-28 + q-27 - 2q-26 - 2q-25 + 2q-24 + 2q-23 - 2q-22 - 2q-21 + 2q-20 + 2q-19 - 2q-18 - q-17 + 2q-16 + q-15 - 3q-14 + 2q-12 - 3q-10 + q-9 + 2q-8 - q-7 - 2q-6 + 2q-5 + 3q-4 - 2q-3 - 2q-2 + 4 - q - 2q2 - q3 + 3q4 - q6 - 2q7 + 2q8 - q11 + q12
4 q-60 - q-59 - q-58 + 3q-55 - q-54 - q-53 - q-52 - 2q-51 + 5q-50 - q-48 - q-47 - 4q-46 + 5q-45 - 5q-41 + 5q-40 - 5q-36 + 6q-35 - q-33 - q-32 - 6q-31 + 8q-30 + q-29 - 2q-28 - 2q-27 - 7q-26 + 10q-25 + 3q-24 - 3q-23 - 3q-22 - 8q-21 + 11q-20 + 5q-19 - 4q-18 - 4q-17 - 8q-16 + 11q-15 + 6q-14 - 5q-13 - 5q-12 - 8q-11 + 12q-10 + 7q-9 - 6q-8 - 6q-7 - 8q-6 + 12q-5 + 7q-4 - 4q-3 - 5q-2 - 9q-1 + 10 + 6q - 2q2 - 3q3 - 7q4 + 7q5 + 3q6 - q7 - q8 - 5q9 + 4q10 + q11 - 3q14 + 2q15 - q19 + q20
5 q-90 - q-89 - q-88 + q-85 + 2q-84 - 2q-82 - q-81 - q-80 + 3q-78 + 2q-77 - q-76 - 2q-75 - 2q-74 - q-73 + 2q-72 + 3q-71 - q-69 - 2q-68 - q-67 + q-66 + 2q-65 + q-64 - q-63 - 2q-62 - q-61 + q-60 + 3q-59 + q-58 - 2q-57 - 3q-56 - 2q-55 + q-54 + 5q-53 + 3q-52 - 2q-51 - 5q-50 - 4q-49 + q-48 + 6q-47 + 6q-46 - 7q-44 - 7q-43 + 6q-41 + 8q-40 + 2q-39 - 7q-38 - 9q-37 - 2q-36 + 6q-35 + 10q-34 + 3q-33 - 6q-32 - 10q-31 - 4q-30 + 5q-29 + 11q-28 + 4q-27 - 5q-26 - 10q-25 - 6q-24 + 4q-23 + 12q-22 + 5q-21 - 4q-20 - 11q-19 - 7q-18 + 5q-17 + 13q-16 + 7q-15 - 5q-14 - 13q-13 - 7q-12 + 5q-11 + 12q-10 + 9q-9 - 5q-8 - 13q-7 - 7q-6 + 4q-5 + 9q-4 + 9q-3 - 3q-2 - 11q-1 - 5 + 3q + 7q2 + 6q3 - 3q4 - 8q5 - 2q6 + 3q7 + 4q8 + 4q9 - 3q10 - 6q11 + q12 + 2q13 + 2q14 + 2q15 - q16 - 4q17 + q18 + q19 + q21 - 2q23 + q24 - q29 + q30
6 q-126 - q-125 - q-124 + q-121 + 3q-119 - q-118 - 2q-117 - q-116 - q-115 - q-113 + 6q-112 - q-110 - q-109 - 2q-108 - q-107 - 4q-106 + 7q-105 + q-104 - q-101 - q-100 - 6q-99 + 7q-98 - 7q-92 + 7q-91 + q-89 - q-87 - q-86 - 8q-85 + 7q-84 + 4q-82 + 2q-81 - q-80 - 2q-79 - 11q-78 + 5q-77 - q-76 + 7q-75 + 5q-74 + q-73 - q-72 - 14q-71 + q-70 - 4q-69 + 8q-68 + 7q-67 + 4q-66 + 2q-65 - 15q-64 - q-63 - 7q-62 + 7q-61 + 7q-60 + 6q-59 + 6q-58 - 15q-57 - q-56 - 9q-55 + 5q-54 + 5q-53 + 5q-52 + 9q-51 - 13q-50 - 9q-48 + 4q-47 + 2q-46 + 3q-45 + 11q-44 - 10q-43 + 2q-42 - 9q-41 + 3q-40 - q-39 + 14q-37 - 7q-36 + 3q-35 - 9q-34 + 2q-33 - 4q-32 - 2q-31 + 16q-30 - 5q-29 + 3q-28 - 10q-27 + q-26 - 5q-25 - 2q-24 + 18q-23 - 4q-22 + 2q-21 - 11q-20 - 5q-18 - q-17 + 20q-16 - 3q-15 + 3q-14 - 12q-13 - q-12 - 6q-11 - 2q-10 + 18q-9 - 3q-8 + 6q-7 - 9q-6 - 6q-4 - 3q-3 + 13q-2 - 5q-1 + 6 - 6q + 3q2 - 3q3 - 2q4 + 8q5 - 8q6 + 3q7 - 5q8 + 5q9 + q10 + 5q12 - 9q13 + q14 - 4q15 + 5q16 + 2q17 + q18 + 3q19 - 7q20 + q21 - 3q22 + 3q23 + q24 + q25 + 2q26 - 4q27 + 2q28 - 2q29 + q30 + q33 - 2q34 + 2q35 - q36 - q41 + q42


Computer Talk. The data above can be recomputed by Mathematica using the package KnotTheory`. Following setup, the sample Mathematica session below reproduces most of the above data (Mathematica system prompts in blue, human input in red, Mathematica output in black):

In[1]:=    
<< KnotTheory`
Loading KnotTheory` (version of August 30, 2005, 10:15:35)...
In[2]:=
PD[Knot[8, 1]]
Out[2]=   
PD[X[1, 4, 2, 5], X[9, 12, 10, 13], X[3, 11, 4, 10], X[11, 3, 12, 2], 
 
>   X[5, 16, 6, 1], X[7, 14, 8, 15], X[13, 8, 14, 9], X[15, 6, 16, 7]]
In[3]:=
GaussCode[Knot[8, 1]]
Out[3]=   
GaussCode[-1, 4, -3, 1, -5, 8, -6, 7, -2, 3, -4, 2, -7, 6, -8, 5]
In[4]:=
DTCode[Knot[8, 1]]
Out[4]=   
DTCode[4, 10, 16, 14, 12, 2, 8, 6]
In[5]:=
br = BR[Knot[8, 1]]
Out[5]=   
BR[5, {-1, -1, -2, 1, -2, -3, 2, 4, -3, 4}]
In[6]:=
{First[br], Crossings[br]}
Out[6]=   
{5, 10}
In[7]:=
BraidIndex[Knot[8, 1]]
Out[7]=   
5
In[8]:=
Show[DrawMorseLink[Knot[8, 1]]]
Out[8]=   
 -Graphics- 
In[9]:=
#[Knot[8, 1]]& /@ {SymmetryType, UnknottingNumber, ThreeGenus, BridgeIndex, SuperBridgeIndex, NakanishiIndex}
Out[9]=   
{Reversible, 1, 1, 2, {4, 5}, 1}
In[10]:=
alex = Alexander[Knot[8, 1]][t]
Out[10]=   
    3
7 - - - 3 t
    t
In[11]:=
Conway[Knot[8, 1]][z]
Out[11]=   
       2
1 - 3 z
In[12]:=
Select[AllKnots[], (alex === Alexander[#][t])&]
Out[12]=   
{Knot[8, 1]}
In[13]:=
{KnotDet[Knot[8, 1]], KnotSignature[Knot[8, 1]]}
Out[13]=   
{13, 0}
In[14]:=
Jones[Knot[8, 1]][q]
Out[14]=   
     -6    -5    -4   2    2    2        2
2 + q   - q   + q   - -- + -- - - - q + q
                       3    2   q
                      q    q
In[15]:=
Select[AllKnots[], (J === Jones[#][q] || (J /. q-> 1/q) === Jones[#][q])&]
Out[15]=   
{Knot[8, 1], Knot[11, NonAlternating, 70]}
In[16]:=
A2Invariant[Knot[8, 1]][q]
Out[16]=   
 -20    -18    -12    -10    2    6    8
q    + q    - q    - q    + q  + q  + q
In[17]:=
HOMFLYPT[Knot[8, 1]][a, z]
Out[17]=   
 -2    4    6    2    2  2    4  2
a   - a  + a  - z  - a  z  - a  z
In[18]:=
Kauffman[Knot[8, 1]][a, z]
Out[18]=   
                                    2                        3
  -2    4    6      3        5     z       4  2      6  2   z       3
-a   - a  - a  - 3 a  z - 3 a  z + -- + 7 a  z  + 6 a  z  + -- - a z  + 
                                    2                       a
                                   a
 
       3  3      5  3    4      2  4      4  4      6  4      5      3  5
>   5 a  z  + 7 a  z  + z  - 2 a  z  - 8 a  z  - 5 a  z  + a z  - 4 a  z  - 
 
       5  5    2  6      4  6    6  6    3  7    5  7
>   5 a  z  + a  z  + 2 a  z  + a  z  + a  z  + a  z
In[19]:=
{Vassiliev[2][Knot[8, 1]], Vassiliev[3][Knot[8, 1]]}
Out[19]=   
{-3, 3}
In[20]:=
Kh[Knot[8, 1]][q, t]
Out[20]=   
1           1        1       1       1       1       1       1      1      1
- + 2 q + ------ + ----- + ----- + ----- + ----- + ----- + ----- + ---- + --- + 
q          13  6    9  5    9  4    7  3    5  3    5  2    3  2    3     q t
          q   t    q  t    q  t    q  t    q  t    q  t    q  t    q  t
 
           5  2
>   q t + q  t
In[21]:=
ColouredJones[Knot[8, 1], 2][q]
Out[21]=   
     -18    -17    -16    2     -14    2     3     3    3    3    3     -5
2 + q    - q    - q    + --- - q    - --- + --- - --- + -- - -- + -- + q   - 
                          15           13    12    10    9    7    6
                         q            q     q     q     q    q    q
 
    3    2     -2   3      2      3    5    6
>   -- + -- + q   - - - 2 q  + 2 q  - q  + q
     4    3         q
    q    q


Dror Bar-Natan: The Knot Atlas: The Rolfsen Knot Table: The Knot 81
7.7
77
8.2
82