8 7

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8 6.gif

8_6

8 8.gif

8_8

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8 7 Quick Notes


8 7 Further Notes and Views

Knot presentations

Planar diagram presentation X1425 X3,10,4,11 X11,1,12,16 X5,13,6,12 X7,15,8,14 X13,7,14,6 X15,9,16,8 X9,2,10,3
Gauss code -1, 8, -2, 1, -4, 6, -5, 7, -8, 2, -3, 4, -6, 5, -7, 3
Dowker-Thistlethwaite code 4 10 12 14 2 16 6 8
Conway Notation [4112]

Three dimensional invariants

Symmetry type Reversible
Unknotting number 1
3-genus 3
Bridge index 2
Super bridge index [math]\displaystyle{ \{3,6\} }[/math]
Nakanishi index 1
Maximal Thurston-Bennequin number [-2][-8]
Hyperbolic Volume 7.0222
A-Polynomial See Data:8 7/A-polynomial

[edit Notes for 8 7's three dimensional invariants]

Four dimensional invariants

Smooth 4 genus [math]\displaystyle{ 1 }[/math]
Topological 4 genus [math]\displaystyle{ 1 }[/math]
Concordance genus [math]\displaystyle{ 3 }[/math]
Rasmussen s-Invariant 2

[edit Notes for 8 7's four dimensional invariants]

Polynomial invariants

Alexander polynomial [math]\displaystyle{ t^3-3 t^2+5 t-5+5 t^{-1} -3 t^{-2} + t^{-3} }[/math]
Conway polynomial [math]\displaystyle{ z^6+3 z^4+2 z^2+1 }[/math]
2nd Alexander ideal (db, data sources) [math]\displaystyle{ \{1\} }[/math]
Determinant and Signature { 23, 2 }
Jones polynomial [math]\displaystyle{ -q^6+2 q^5-3 q^4+4 q^3-4 q^2+4 q-2+2 q^{-1} - q^{-2} }[/math]
HOMFLY-PT polynomial (db, data sources) [math]\displaystyle{ z^6 a^{-2} +5 z^4 a^{-2} -z^4 a^{-4} -z^4+8 z^2 a^{-2} -3 z^2 a^{-4} -3 z^2+4 a^{-2} -2 a^{-4} -1 }[/math]
Kauffman polynomial (db, data sources) [math]\displaystyle{ z^7 a^{-1} +z^7 a^{-3} +4 z^6 a^{-2} +2 z^6 a^{-4} +2 z^6+a z^5-z^5 a^{-1} +2 z^5 a^{-5} -12 z^4 a^{-2} -3 z^4 a^{-4} +2 z^4 a^{-6} -7 z^4-3 a z^3-3 z^3 a^{-1} -2 z^3 a^{-3} -z^3 a^{-5} +z^3 a^{-7} +12 z^2 a^{-2} +4 z^2 a^{-4} -2 z^2 a^{-6} +6 z^2+a z+2 z a^{-1} +2 z a^{-3} -z a^{-7} -4 a^{-2} -2 a^{-4} -1 }[/math]
The A2 invariant [math]\displaystyle{ -q^6+1+2 q^{-2} +2 q^{-6} + q^{-10} - q^{-14} - q^{-18} }[/math]
The G2 invariant [math]\displaystyle{ q^{32}-q^{30}+2 q^{28}-3 q^{26}+q^{24}-q^{22}-3 q^{20}+7 q^{18}-8 q^{16}+5 q^{14}-3 q^{12}-2 q^{10}+6 q^8-10 q^6+7 q^4-3 q^2+6 q^{-2} -6 q^{-4} +4 q^{-6} +3 q^{-8} - q^{-10} +4 q^{-12} -4 q^{-14} +2 q^{-16} +4 q^{-18} -5 q^{-20} +10 q^{-22} -7 q^{-24} +5 q^{-26} +3 q^{-28} -7 q^{-30} +10 q^{-32} -11 q^{-34} +8 q^{-36} -2 q^{-38} -3 q^{-40} +8 q^{-42} -8 q^{-44} +6 q^{-46} -3 q^{-50} +3 q^{-52} -3 q^{-54} - q^{-56} +4 q^{-58} -5 q^{-60} +5 q^{-62} -3 q^{-64} -2 q^{-66} +4 q^{-68} -7 q^{-70} +5 q^{-72} -5 q^{-74} +2 q^{-76} - q^{-78} -3 q^{-80} +4 q^{-82} -4 q^{-84} +4 q^{-86} -2 q^{-88} + q^{-90} -2 q^{-94} +2 q^{-96} - q^{-98} + q^{-100} }[/math]

Vassiliev invariants

V2 and V3: (2, 2)
V2,1 through V6,9:
V2,1 V3,1 V4,1 V4,2 V4,3 V5,1 V5,2 V5,3 V5,4 V6,1 V6,2 V6,3 V6,4 V6,5 V6,6 V6,7 V6,8 V6,9
[math]\displaystyle{ 8 }[/math] [math]\displaystyle{ 16 }[/math] [math]\displaystyle{ 32 }[/math] [math]\displaystyle{ \frac{124}{3} }[/math] [math]\displaystyle{ -\frac{28}{3} }[/math] [math]\displaystyle{ 128 }[/math] [math]\displaystyle{ \frac{448}{3} }[/math] [math]\displaystyle{ \frac{64}{3} }[/math] [math]\displaystyle{ -16 }[/math] [math]\displaystyle{ \frac{256}{3} }[/math] [math]\displaystyle{ 128 }[/math] [math]\displaystyle{ \frac{992}{3} }[/math] [math]\displaystyle{ -\frac{224}{3} }[/math] [math]\displaystyle{ \frac{7951}{15} }[/math] [math]\displaystyle{ \frac{1052}{5} }[/math] [math]\displaystyle{ -\frac{6596}{45} }[/math] [math]\displaystyle{ \frac{65}{9} }[/math] [math]\displaystyle{ -\frac{929}{15} }[/math]

V2,1 through V6,9 were provided by Petr Dunin-Barkowski <barkovs@itep.ru>, Andrey Smirnov <asmirnov@itep.ru>, and Alexei Sleptsov <sleptsov@itep.ru> and uploaded on October 2010 by User:Drorbn. Note that they are normalized differently than V2 and V3.

Khovanov Homology

The coefficients of the monomials [math]\displaystyle{ t^rq^j }[/math] are shown, along with their alternating sums [math]\displaystyle{ \chi }[/math] (fixed [math]\displaystyle{ j }[/math], alternation over [math]\displaystyle{ r }[/math]). The squares with yellow highlighting are those on the "critical diagonals", where [math]\displaystyle{ j-2r=s+1 }[/math] or [math]\displaystyle{ j-2r=s+1 }[/math], where [math]\displaystyle{ s= }[/math]2 is the signature of 8 7. Nonzero entries off the critical diagonals (if any exist) are highlighted in red.

\ r
  \  
j \
-3-2-1012345χ
13        1-1
11       1 1
9      21 -1
7     21  1
5    22   0
3   22    0
1  13     2
-1 11      0
-3 1       1
-51        -1

Computer Talk

Much of the above data can be recomputed by Mathematica using the package KnotTheory`. See A Sample KnotTheory` Session.

[math]\displaystyle{ \textrm{Include}(\textrm{ColouredJonesM.mhtml}) }[/math]

In[1]:=    
<< KnotTheory`
Loading KnotTheory` (version of August 17, 2005, 14:44:34)...
In[2]:=
Crossings[Knot[8, 7]]
Out[2]=  
8
In[3]:=
PD[Knot[8, 7]]
Out[3]=  
PD[X[1, 4, 2, 5], X[3, 10, 4, 11], X[11, 1, 12, 16], X[5, 13, 6, 12], 
  X[7, 15, 8, 14], X[13, 7, 14, 6], X[15, 9, 16, 8], X[9, 2, 10, 3]]
In[4]:=
GaussCode[Knot[8, 7]]
Out[4]=  
GaussCode[-1, 8, -2, 1, -4, 6, -5, 7, -8, 2, -3, 4, -6, 5, -7, 3]
In[5]:=
BR[Knot[8, 7]]
Out[5]=  
BR[3, {1, 1, 1, 1, -2, 1, -2, -2}]
In[6]:=
alex = Alexander[Knot[8, 7]][t]
Out[6]=  
      -3   3    5            2    3

-5 + t - -- + - + 5 t - 3 t + t

           2   t
t
In[7]:=
Conway[Knot[8, 7]][z]
Out[7]=  
       2      4    6
1 + 2 z  + 3 z  + z
In[8]:=
Select[AllKnots[], (alex === Alexander[#][t])&]
Out[8]=  
{Knot[8, 7], Knot[11, NonAlternating, 24]}
In[9]:=
{KnotDet[Knot[8, 7]], KnotSignature[Knot[8, 7]]}
Out[9]=  
{23, 2}
In[10]:=
J=Jones[Knot[8, 7]][q]
Out[10]=  
      -2   2            2      3      4      5    6

-2 - q + - + 4 q - 4 q + 4 q - 3 q + 2 q - q

q
In[11]:=
Select[AllKnots[], (J === Jones[#][q] || (J /. q-> 1/q) === Jones[#][q])&]
Out[11]=  
{Knot[8, 7]}
In[12]:=
A2Invariant[Knot[8, 7]][q]
Out[12]=  
     -6      2      6    10    14    18
1 - q   + 2 q  + 2 q  + q   - q   - q
In[13]:=
Kauffman[Knot[8, 7]][a, z]
Out[13]=  
                                                2      2       2    3
    2    4    z    2 z   2 z            2   2 z    4 z    12 z    z

-1 - -- - -- - -- + --- + --- + a z + 6 z - ---- + ---- + ----- + -- -

     4    2    7    3     a                   6      4      2      7
    a    a    a    a                         a      a      a      a

  3      3      3                      4      4       4      5    5
 z    2 z    3 z         3      4   2 z    3 z    12 z    2 z    z
 -- - ---- - ---- - 3 a z  - 7 z  + ---- - ---- - ----- + ---- - -- + 
  5     3     a                       6      4      2       5    a
 a     a                             a      a      a       a

                  6      6    7    7
    5      6   2 z    4 z    z    z
 a z  + 2 z  + ---- + ---- + -- + --
                 4      2     3   a
a a a
In[14]:=
{Vassiliev[2][Knot[8, 7]], Vassiliev[3][Knot[8, 7]]}
Out[14]=  
{0, 2}
In[15]:=
Kh[Knot[8, 7]][q, t]
Out[15]=  
         3     1       1      1      1    q      3        5

3 q + 2 q + ----- + ----- + ---- + --- + - + 2 q t + 2 q t +

             5  3    3  2      2   q t   t
            q  t    q  t    q t

    5  2      7  2    7  3      9  3    9  4    11  4    13  5
2 q t + 2 q t + q t + 2 q t + q t + q t + q t