5 1

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4 1.gif

4_1

5 2.gif

5_2

5 1.gif Visit 5 1's page at the Knot Server (KnotPlot driven, includes 3D interactive images!)

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An interlaced pentagram, this is known variously as the "Cinquefoil Knot", after certain herbs and shrubs of the rose family which have 5-lobed leaves and 5-petaled flowers (see e.g. [4]),

as the "Pentafoil Knot" (visit Bert Jagers' pentafoil page), as the "Double Overhand Knot", as 5_1, or finally as the torus knot T(5,2).

When taken off the post the strangle knot (hitch) of practical knot tying deforms to 5_1




A kolam of a 2x3 dot array
The VISA Interlink Logo [1]
Version of the US bicentennial emblem
A pentagonal table by Bob Mackay [2]
The Utah State Parks logo
As impossible object ("Penrose" pentagram)
Folded ribbon which is single-sided (more complex version of Möbius Strip).
Non-pentagonal shape.
Pentagram of circles.
Alternate pentagram of intersecting circles.
3D-looking rendition.
Partial view of US bicentennial logo on a shirt seen in Lisboa [3]
Non-prime knot with two 5_1 configurations on a closed loop.
Knotted epitrochoid
Sum of two 5_1s, Vienna, orthodox church

This sentence was last edited by Dror. Sometime later, Scott added this sentence.

Knot presentations

Planar diagram presentation X1627 X3849 X5,10,6,1 X7283 X9,4,10,5
Gauss code -1, 4, -2, 5, -3, 1, -4, 2, -5, 3
Dowker-Thistlethwaite code 6 8 10 2 4
Conway Notation [5]

Three dimensional invariants

Symmetry type Reversible
Unknotting number 2
3-genus 2
Bridge index 2
Super bridge index 3
Nakanishi index 1
Maximal Thurston-Bennequin number [-10][3]
Hyperbolic Volume Not hyperbolic
A-Polynomial See Data:5 1/A-polynomial

[edit Notes for 5 1's three dimensional invariants]

Four dimensional invariants

Smooth 4 genus [math]\displaystyle{ 2 }[/math]
Topological 4 genus [math]\displaystyle{ 2 }[/math]
Concordance genus [math]\displaystyle{ \textrm{ConcordanceGenus}(\textrm{Knot}(5,1)) }[/math]
Rasmussen s-Invariant -4

[edit Notes for 5 1's four dimensional invariants]

Polynomial invariants

Alexander polynomial [math]\displaystyle{ t^2+ t^{-2} -t- t^{-1} +1 }[/math]
Conway polynomial [math]\displaystyle{ z^4+3 z^2+1 }[/math]
2nd Alexander ideal (db, data sources) [math]\displaystyle{ \{1\} }[/math]
Determinant and Signature { 5, -4 }
Jones polynomial [math]\displaystyle{ - q^{-7} + q^{-6} - q^{-5} + q^{-4} + q^{-2} }[/math]
HOMFLY-PT polynomial (db, data sources) [math]\displaystyle{ a^6 \left(-z^2\right)-2 a^6+a^4 z^4+4 a^4 z^2+3 a^4 }[/math]
Kauffman polynomial (db, data sources) [math]\displaystyle{ a^9 z+a^8 z^2+a^7 z^3-a^7 z+a^6 z^4-3 a^6 z^2+2 a^6+a^5 z^3-2 a^5 z+a^4 z^4-4 a^4 z^2+3 a^4 }[/math]
The A2 invariant [math]\displaystyle{ -q^{22}-q^{20}-q^{18}+q^{14}+q^{12}+2 q^{10}+q^8+q^6 }[/math]
The G2 invariant [math]\displaystyle{ q^{120}-q^{100}-q^{98}-q^{92}-q^{90}-q^{88}-q^{82}-q^{80}-q^{78}-q^{72}+q^{58}+q^{56}+q^{52}+2 q^{50}+q^{48}+q^{46}+q^{44}+q^{42}+2 q^{40}+q^{38}+q^{34}+q^{32}+q^{30} }[/math]

Vassiliev invariants

V2 and V3: (3, -5)
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{ 12 }[/math] [math]\displaystyle{ -40 }[/math] [math]\displaystyle{ 72 }[/math] [math]\displaystyle{ 174 }[/math] [math]\displaystyle{ 26 }[/math] [math]\displaystyle{ -480 }[/math] [math]\displaystyle{ -\frac{2512}{3} }[/math] [math]\displaystyle{ -\frac{448}{3} }[/math] [math]\displaystyle{ -104 }[/math] [math]\displaystyle{ 288 }[/math] [math]\displaystyle{ 800 }[/math] [math]\displaystyle{ 2088 }[/math] [math]\displaystyle{ 312 }[/math] [math]\displaystyle{ \frac{41151}{10} }[/math] [math]\displaystyle{ \frac{2494}{15} }[/math] [math]\displaystyle{ \frac{7634}{5} }[/math] [math]\displaystyle{ \frac{43}{2} }[/math] [math]\displaystyle{ \frac{1951}{10} }[/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]-4 is the signature of 5 1. Nonzero entries off the critical diagonals (if any exist) are highlighted in red.

\ r
  \  
j \
-5-4-3-2-10χ
-3     11
-5     11
-7   1  1
-9      0
-11 11   0
-13      0
-151     -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[5, 1]]
Out[2]=  
5
In[3]:=
PD[Knot[5, 1]]
Out[3]=  
PD[X[1, 6, 2, 7], X[3, 8, 4, 9], X[5, 10, 6, 1], X[7, 2, 8, 3], 
  X[9, 4, 10, 5]]
In[4]:=
GaussCode[Knot[5, 1]]
Out[4]=  
GaussCode[-1, 4, -2, 5, -3, 1, -4, 2, -5, 3]
In[5]:=
BR[Knot[5, 1]]
Out[5]=  
BR[2, {-1, -1, -1, -1, -1}]
In[6]:=
alex = Alexander[Knot[5, 1]][t]
Out[6]=  
     -2   1        2

1 + t - - - t + t

t
In[7]:=
Conway[Knot[5, 1]][z]
Out[7]=  
       2    4
1 + 3 z  + z
In[8]:=
Select[AllKnots[], (alex === Alexander[#][t])&]
Out[8]=  
{Knot[5, 1], Knot[10, 132]}
In[9]:=
{KnotDet[Knot[5, 1]], KnotSignature[Knot[5, 1]]}
Out[9]=  
{5, -4}
In[10]:=
J=Jones[Knot[5, 1]][q]
Out[10]=  
  -7    -6    -5    -4    -2
-q   + q   - q   + q   + q
In[11]:=
Select[AllKnots[], (J === Jones[#][q] || (J /. q-> 1/q) === Jones[#][q])&]
Out[11]=  
{Knot[5, 1], Knot[10, 132]}
In[12]:=
A2Invariant[Knot[5, 1]][q]
Out[12]=  
  -22    -20    -18    -14    -12    2     -8    -6

-q - q - q + q + q + --- + q + q

                                    10
q
In[13]:=
Kauffman[Knot[5, 1]][a, z]
Out[13]=  
   4      6      5      7      9        4  2      6  2    8  2

3 a + 2 a - 2 a z - a z + a z - 4 a z - 3 a z + a z +

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

q + q + ------ + ------ + ------ + -----

            15  5    11  4    11  3    7  2
q t q t q t q t