© | Dror Bar-Natan: The Knot Atlas: 11 Crossing Knots:
K11a20
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K11a21
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   The Knot K11a21

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Acknowledgement

K11a21 as Morse Link
DrawMorseLink

PD Presentation: X4251 X8493 X12,6,13,5 X2837 X18,9,19,10 X6,12,7,11 X22,14,1,13 X20,16,21,15 X10,17,11,18 X16,20,17,19 X14,22,15,21

Gauss Code: {1, -4, 2, -1, 3, -6, 4, -2, 5, -9, 6, -3, 7, -11, 8, -10, 9, -5, 10, -8, 11, -7}

DT (Dowker-Thistlethwaite) Code: 4 8 12 2 18 6 22 20 10 16 14

Alexander Polynomial: - 5t-2 + 19t-1 - 27 + 19t - 5t2

Conway Polynomial: 1 - z2 - 5z4

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

Determinant and Signature: {75, 2}

Jones Polynomial: q-1 - 2 + 5q - 7q2 + 10q3 - 12q4 + 11q5 - 10q6 + 8q7 - 5q8 + 3q9 - q10

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

A2 (sl(3)) Invariant: q-4 + 3q2 - q4 + q6 + 2q8 - 2q10 - 2q14 - q16 - 2q20 + 3q22 + q24 + 2q28 - q30 - q32

HOMFLY-PT Polynomial: - a-10 + 3a-8 + 3a-8z2 - 2a-6 - 3a-6z2 - 2a-6z4 - a-4 - 2a-4z2 - 2a-4z4 + a-2 - a-2z4 + 1 + z2

Kauffman Polynomial: - a-11z + 4a-11z3 - 4a-11z5 + a-11z7 + a-10 - 7a-10z2 + 16a-10z4 - 13a-10z6 + 3a-10z8 + 3a-9z3 + 5a-9z5 - 10a-9z7 + 3a-9z9 + 3a-8 - 22a-8z2 + 42a-8z4 - 29a-8z6 + 4a-8z8 + a-8z10 + 6a-7z - 16a-7z3 + 24a-7z5 - 21a-7z7 + 6a-7z9 + 2a-6 - 16a-6z2 + 28a-6z4 - 21a-6z6 + 4a-6z8 + a-6z10 + 7a-5z - 15a-5z3 + 12a-5z5 - 7a-5z7 + 3a-5z9 - a-4 + 3a-4z2 - 2a-4z4 - 2a-4z6 + 3a-4z8 + 2a-3z - 2a-3z3 - a-3z5 + 3a-3z7 - a-2 + 2a-2z2 - 3a-2z4 + 3a-2z6 - 2a-1z3 + 2a-1z5 + 1 - 2z2 + z4

V2 and V3, the type 2 and 3 Vassiliev invariants: {-1, -1}

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=2 is the signature of 1121. Nonzero entries off the critical diagonals (if any exist) are highlighted in red.)
  
trqj r = -2r = -1r = 0r = 1r = 2r = 3r = 4r = 5r = 6r = 7r = 8r = 9
j = 21           1
j = 19          2 
j = 17         31 
j = 15        52  
j = 13       53   
j = 11      65    
j = 9     65     
j = 7    46      
j = 5   36       
j = 3  24        
j = 1 14         
j = -1 1          
j = -31           


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]:=
Show[DrawMorseLink[Knot[11, Alternating, 21]]]
Out[2]=   
 -Graphics- 
In[3]:=
PD[Knot[11, Alternating, 21]]
Out[3]=   
PD[X[4, 2, 5, 1], X[8, 4, 9, 3], X[12, 6, 13, 5], X[2, 8, 3, 7], 
 
>   X[18, 9, 19, 10], X[6, 12, 7, 11], X[22, 14, 1, 13], X[20, 16, 21, 15], 
 
>   X[10, 17, 11, 18], X[16, 20, 17, 19], X[14, 22, 15, 21]]
In[4]:=
GaussCode[Knot[11, Alternating, 21]]
Out[4]=   
GaussCode[1, -4, 2, -1, 3, -6, 4, -2, 5, -9, 6, -3, 7, -11, 8, -10, 9, -5, 10, 
 
>   -8, 11, -7]
In[5]:=
DTCode[Knot[11, Alternating, 21]]
Out[5]=   
DTCode[4, 8, 12, 2, 18, 6, 22, 20, 10, 16, 14]
In[6]:=
alex = Alexander[Knot[11, Alternating, 21]][t]
Out[6]=   
      5    19             2
-27 - -- + -- + 19 t - 5 t
       2   t
      t
In[7]:=
Conway[Knot[11, Alternating, 21]][z]
Out[7]=   
     2      4
1 - z  - 5 z
In[8]:=
Select[AllKnots[], (alex === Alexander[#][t])&]
Out[8]=   
{Knot[11, Alternating, 21]}
In[9]:=
{KnotDet[Knot[11, Alternating, 21]], KnotSignature[Knot[11, Alternating, 21]]}
Out[9]=   
{75, 2}
In[10]:=
J=Jones[Knot[11, Alternating, 21]][q]
Out[10]=   
     1            2       3       4       5       6      7      8      9    10
-2 + - + 5 q - 7 q  + 10 q  - 12 q  + 11 q  - 10 q  + 8 q  - 5 q  + 3 q  - q
     q
In[11]:=
Select[AllKnots[], (J === Jones[#][q] || (J /. q-> 1/q) === Jones[#][q])&]
Out[11]=   
{Knot[11, Alternating, 21]}
In[12]:=
A2Invariant[Knot[11, Alternating, 21]][q]
Out[12]=   
 -4      2    4    6      8      10      14    16      20      22    24
q   + 3 q  - q  + q  + 2 q  - 2 q   - 2 q   - q   - 2 q   + 3 q   + q   + 
 
       28    30    32
>   2 q   - q   - q
In[13]:=
HOMFLYPT[Knot[11, Alternating, 21]][a, z]
Out[13]=   
                                         2      2      2      4      4    4
     -10   3    2     -4    -2    2   3 z    3 z    2 z    2 z    2 z    z
1 - a    + -- - -- - a   + a   + z  + ---- - ---- - ---- - ---- - ---- - --
            8    6                      8      6      4      6      4     2
           a    a                      a      a      a      a      a     a
In[14]:=
Kauffman[Knot[11, Alternating, 21]][a, z]
Out[14]=   
                                                                   2       2
     -10   3    2     -4    -2    z    6 z   7 z   2 z      2   7 z    22 z
1 + a    + -- + -- - a   - a   - --- + --- + --- + --- - 2 z  - ---- - ----- - 
            8    6                11    7     5     3            10      8
           a    a                a     a     a     a            a       a
 
        2      2      2      3      3       3       3      3      3
    16 z    3 z    2 z    4 z    3 z    16 z    15 z    2 z    2 z     4
>   ----- + ---- + ---- + ---- + ---- - ----- - ----- - ---- - ---- + z  + 
      6       4      2     11      9      7       5       3     a
     a       a      a     a       a      a       a       a
 
        4       4       4      4      4      5      5       5       5    5
    16 z    42 z    28 z    2 z    3 z    4 z    5 z    24 z    12 z    z
>   ----- + ----- + ----- - ---- - ---- - ---- + ---- + ----- + ----- - -- + 
      10      8       6       4      2     11      9      7       5      3
     a       a       a       a      a     a       a      a       a      a
 
       5       6       6       6      6      6    7        7       7      7
    2 z    13 z    29 z    21 z    2 z    3 z    z     10 z    21 z    7 z
>   ---- - ----- - ----- - ----- - ---- + ---- + --- - ----- - ----- - ---- + 
     a       10      8       6       4      2     11     9       7       5
            a       a       a       a      a     a      a       a       a
 
       7      8      8      8      8      9      9      9    10    10
    3 z    3 z    4 z    4 z    3 z    3 z    6 z    3 z    z     z
>   ---- + ---- + ---- + ---- + ---- + ---- + ---- + ---- + --- + ---
      3     10      8      6      4      9      7      5     8     6
     a     a       a      a      a      a      a      a     a     a
In[15]:=
{Vassiliev[2][Knot[11, Alternating, 21]], Vassiliev[3][Knot[11, Alternating, 21]]}
Out[15]=   
{-1, -1}
In[16]:=
Kh[Knot[11, Alternating, 21]][q, t]
Out[16]=   
         3     1      1    q      3        5        5  2      7  2      7  3
4 q + 2 q  + ----- + --- + - + 4 q  t + 3 q  t + 6 q  t  + 4 q  t  + 6 q  t  + 
              3  2   q t   t
             q  t
 
       9  3      9  4      11  4      11  5      13  5      13  6      15  6
>   6 q  t  + 5 q  t  + 6 q   t  + 5 q   t  + 5 q   t  + 3 q   t  + 5 q   t  + 
 
       15  7      17  7    17  8      19  8    21  9
>   2 q   t  + 3 q   t  + q   t  + 2 q   t  + q   t


Dror Bar-Natan: The Knot Atlas: 11 Crossing Knots: The Knot K11a21
K11a20
K11a20
K11a22
K11a22