4 1

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3_1

5_1

Contents

Image:4 1.gif
(KnotPlot image)

See the full Rolfsen Knot Table.

Visit 4 1's page at the Knot Server (KnotPlot driven, includes 3D interactive images!)

Visit 4_1's page at Knotilus!

Visit 4 1's page at the original Knot Atlas!

4_1 is also known as "the Figure Eight knot", as some people think it looks like a figure `8' in one of its common projections. See e.g. [3], [4].

A Neli-Kolam with 3x2 dot array[1]
A Neli-Kolam with 3x2 dot array[1]
Thurston's Trick [2]
Thurston's Trick [2]

[edit] Knot presentations

Planar diagram presentation X4251 X8615 X6374 X2738
Gauss code 1, -4, 3, -1, 2, -3, 4, -2
Dowker-Thistlethwaite code 4 6 8 2
Conway Notation [22]


Minimum Braid Representative A Morse Link Presentation An Arc Presentation
Image:BraidPart3.gifImage:BraidPart0.gifImage:BraidPart3.gifImage:BraidPart0.gif
Image:BraidPart4.gifImage:BraidPart1.gifImage:BraidPart4.gifImage:BraidPart1.gif
Image:BraidPart0.gifImage:BraidPart2.gifImage:BraidPart0.gifImage:BraidPart2.gif

Length is 4, width is 3,

Braid index is 3

Image:4 1_ML.gif Image:4 1_AP.gif
[{3, 5}, {6, 4}, {5, 2}, {1, 3}, {2, 6}, {4, 1}]

[edit Notes on presentations of 4 1]

Knot 4_1.
Knot 4_1.
A graph, knot 4_1.
A graph, knot 4_1.

[edit] Three dimensional invariants

Symmetry type Fully amphicheiral
Unknotting number 1
3-genus 1
Bridge index 2
Super bridge index 3
Nakanishi index 1
Maximal Thurston-Bennequin number [-3][-3]
Hyperbolic Volume 2.02988
A-Polynomial See Data:4 1/A-polynomial

[edit Notes for 4 1's three dimensional invariants]

[edit] Four dimensional invariants

Smooth 4 genus 1
Topological 4 genus 1
Concordance genus 1
Rasmussen s-Invariant 0

[edit Notes for 4 1's four dimensional invariants]

[edit] Polynomial invariants

Alexander polynomial t + 3−t−1
Conway polynomial 1−z2
2nd Alexander ideal (db, data sources) {1}
Determinant and Signature { 5, 0 }
Jones polynomial q2q + 1−q−1 + q−2
HOMFLY-PT polynomial (db, data sources) a2z2−1 + a−2
Kauffman polynomial (db, data sources) az3 + z3a−1 + a2z2 + z2a−2 + 2z2azza−1a2a−2−1
The A2 invariant q8 + q6−1 + q−6 + q−8
The G2 invariant q38 + q34q30 + q28 + q26 + q24 + q18 + q16q10q4−1−q−4q−10 + q−16 + q−18 + q−24 + q−26 + q−28q−30 + q−34 + q−38

[edit] "Similar" Knots (within the Atlas)

Same Alexander/Conway Polynomial: {}

Same Jones Polynomial (up to mirroring, q\leftrightarrow q^{-1}): {K11n19,}

[edit] Vassiliev invariants

V2 and V3: (-1, 0)

[edit] Khovanov Homology

The coefficients of the monomials trqj are shown, along with their alternating sums χ (fixed j, alternation over r). 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 4 1. Nonzero entries off the critical diagonals (if any exist) are highlighted in red.   
\ r
  \  
j \
-2-1012χ
5    11
3     0
1  11 0
-1 11  0
-3     0
-51    1
Integral Khovanov Homology

(db, data source)

  
\dim{\mathcal G}_{2r+i}\operatorname{KH}^r_{\mathbb Z} i = −1 i = 1
r = −2 {\mathbb Z}
r = −1 {\mathbb Z}_2 {\mathbb Z}
r = 0 {\mathbb Z} {\mathbb Z}
r = 1 {\mathbb Z}
r = 2 {\mathbb Z}_2 {\mathbb Z}

[edit] The Coloured Jones Polynomials

[edit] Computer Talk

Much of the above data can be recomputed by Mathematica using the package KnotTheory`. See A Sample KnotTheory` Session, or any of the Computer Talk sections above.

[edit] Modifying This Page

Read me first: Modifying Knot Pages

See/edit the Rolfsen Knot Page master template (intermediate).

See/edit the Rolfsen_Splice_Base (expert).

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3_1

5_1

Retrieved from "http://katlas.org/wiki/4_1"
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