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<td
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style="font-weight: bold;">About HAP: Knots and Quandles<br>
</span></big></td>
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<td
style="vertical-align: top; background-color: rgb(255, 255, 255); text-align: center;"><big
style="font-weight: bold;">Knots and Quandles <br>
</big> Sub-package by Cédric FRAGNAUD and Graham ELLIS </td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 255);">A
quandle (Q, ▹) is a non-empty set Q equipped with a binary operation ▹
: Q × Q → Q satisfying the following axioms:<br>
<br>
1/ ∀ a ∈ Q, a ▹ a = a.<br>
2/ ∀ a, b ∈ Q, ∃! c ∈ Q such that a = c ▹ b.<br>
3/ ∀ a, b, c ∈ Q, (a ▹ b) ▹ c = (a ▹ c) ▹ (b ▹ c).<br>
<br>
One can check that for any group G and n ∈ ℤ, the magma (G, ▹) forms a
quandle with the operation x ▹ y = y<sup>-n</sup>xy<sup>n</sup> , ∀ x,
y ∈ G. Such a quandle is called the n-Fold Conjugation Quandle.<br>
<br>
A quandle <em>Q</em> is said to be connected if the inner automorphism
group <em>Inn Q</em> acts transitively on <em>Q</em>. In other words,
<em>Q</em> is connected if and only if for each pair a, b in <em>Q</em>
there are a<sub>1</sub>, a<sub>2</sub>, . . . , a<sub>n</sub> in <em>Q</em>
such that a ▹ a<sub>1</sub> ▹· · · ▹ a<sub>n</sub>
= b.<br>
<br>
A quandle <em>Q</em> is said to be latin if ∀ a, b ∈ <em>Q</em>, ∃ c ∈<em>
Q</em> such that a = b ▹ c. </td>
</tr>
<tr>
<td
style="background-color: rgb(255, 255, 204); vertical-align: top;">gap>
Q:=Quandle(5,21);<br>
<magma with 5 generators><br>
gap> Display(MultiplicationTable(Q));<br>
[ [ 1, 3, 4, 5, 2 ],<br>
[ 3, 2, 5, 1, 4 ],<br>
[ 4, 5, 3, 2, 1 ],<br>
[ 5, 1, 2, 4, 3 ],<br>
[ 2, 4, 1, 3, 5 ] ]<br>
gap> IsConnected(Q);<br>
true<br>
gap> IsLatin(Q);<br>
true </td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 204);">gap>
G:=DihedralGroup(64);;<br>
gap> Q:=ConjugationQuandle(G,1);<br>
<magma with 19 generators><br>
gap> Size(Q);<br>
64<br>
gap> IsConnected(Q);<br>
false<br>
</td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 255);">Let
Q be a set, e an element in Q, G a permutation group, and stigma an
element in G.<br>
Then (Q,G,e,stigma) describes a Quandle Envelope if :<br>
<ul>
<li>G is a transitive group on Q.</li>
</ul>
<ul>
<li>stigma ∈ Z(G<sub>e</sub>), the center of the stabilizer of
e.</li>
</ul>
<ul>
<li>⟨stigma<sup>G</sup>⟩ = G (that is, the smallest normal
subgroup of G containing stigma is all of G).</li>
</ul>
<p style="height: 9px;">From a Quandle Envelope (Q,G,e,stigma),
we can construct a Quandle (Q, ▹):</p>
<p style="margin-top: -1px; height: 18px;">
for all x,y in Q,
x ▹ y=(ŷ(stigma))(x)
, where ŷ ∈ G satisfies ŷ(e)=y.</p>
<p style="margin-top: -1px; height: 18px;">Such a quandle is
connected. This property is used to construct all the connected
quandles of size n.</p>
</td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 204);">gap>
Q:=[1..9];;
e:=2;;
G:=TransitiveGroup(9,15);;
st:=(1,8,7,4,9,5,3,6);;<br>
gap> IsQuandleEnvelope(Q,G,e,st);
QE:=QuandleQuandleEnvelope(Q,G,e,st);<br>
true<br>
<magma with 9 generators><br>
gap> IsQuandle(QE); IsConnected(QE);<br>
true<br>
true<br>
gap> ConnectedQuandles(20); time;<br>
[ <magma with 20 generators>, <magma with 20 generators>,
<magma with 20 generators>, <br>
<magma with 20 generators>, <magma with 20
generators>, <magma with 20 generators>, <br>
<magma with 20 generators>, <magma with 20
generators>, <magma with 20 generators>, <br>
<magma with 20 generators> ]<br>
3364296</td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 255);">Let's
denote
R<sub>x</sub> the mapping defined by R<sub>x</sub> : Q→Q, y ↦y▹x.<br>
We define the right multiplication group G of a quandle Q by G=〈R<sub>x</sub>,
x
∈
Q〉.<br>
We also define the automorphism group Aut(Q)={f:Q→Q}.<br>
It can be proven that R<sub>x</sub> is a subgroup of Aut(Q).</td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 204);">gap>
Q:=ConnectedQuandle(8,2);;
q:=Random(Q);<br>
m6<br>
gap> A:=AutomorphismGroupQuandle(Q);; a:=Random(A);;<br>
gap> q^a;<br>
m4<br>
gap> R:=RightMultiplicationGroupOfQuandle(Q);; r:=Random(R);;<br>
gap> q^r;<br>
m3</td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 255);">A
knot is an embedding of the circle S<sup>1</sup> in ℝ<sup>3</sup>.<br>
<br>
To study these structures, we use knot diagrams, which are projections
of these knots into ℝ<sup>2</sup>, defined, for instance, by f : ℝ<sup>3</sup>
→ ℝ<sup>2</sup>; (x,y,z) → (x,y) subject to the constraint that
the preimage of any (x, y) ∈ ℝ<sup>2</sup> contains at most two points.<br>
<br>
Crossing points occur when the preimage of a point in ℝ<sup>2</sup>
contains more than one point.<br>
<br>
At these crossing points, we denote the point in the preimage that is
nearer to the ℝ<sup>2</sup> plane as the under-crossing point and the
point farther away as the over-crossing point. An arc is a line that
connects two crossing points in the knot diagram, with a line break
occurring when an undercrossing point is mapped to the arc.<br>
<br>
We may give a knot diagram an orientation, i.e. a direction of
travelling around the knot. This allows us to categorize crossings as
either positive or negative:
<div style="text-align: center;"><img
title="A positive and neative crossing"
style="width: 278px; height: 181px;"
src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAARYAAAC1CAMAAACtbCCJAAAAq1BMVEX///8AAABlZWX8/Py8vLz19fXf39/t7e3p6enk5OTy8vKEhIT39/eYmJjQ0ND6+vrExMROTk6ioqJISEheXl7X19epqamLi4t5eXlVVVVvb28tLS0KCgq1tbWPj4/JyckVFRUpKSk0NDQ9PT19fX1ycnIfHx8rKysUFBSlpaUeBwBRWGCpqKB7ip0pAAA6BQA1DgCCjpz7+vCjpKh1goopEAVja2wgAAC0tr5q5yZSAAAHN0lEQVR4nO2daXuqOhCAGVGsKxVU6m7d2t7tLHf9/7/sJohaK0iWGeKHeb/0OYs4fZlBEibR8xiGYRiGYRiGYRiGYRiGYRiGYRiGYRiGYRiGYRiGYRiGYRiGYRiGYRiGYRg6GmRH9p8ukL0JFckz1ZEDuKD6msaCKhovGdYyhgpvsoQ+VSDjXsoY5spaukB2lpaXk9Qr/999oPNyZAcHZS0h0HnJmCppkV5WlGG8QBwoa/FG1F5qMB2oaJGR0HlpvsHG09BC7KVVg4E3UdIiIxkShfEEEHtaWuSVekkUjTz2xFPVIuuoRhJGK7Wip4XwLGVHVtVC5aUJMPY9XS1kXkSuJPKnshZvNCCIRFrJ4tF74THXsQlOV61Yo0gn6PnSOlkxYIh/li7X8n6g8bIJTFHD6K3NrRB4qZt+wsWokfQsckUywfWyM//cx4xEWLEc3gwxry8WVqSXWKfs7rCEg/WRhlBrYsTiSSubusXLY4AWRhg9WLftjzIBwDlLO5j5DxCJyJWu/VFkvqB42cHW9hAv9pF0h7BGsSLHdTCyPUajA1u7XJHUbb10X+GAUEFHnq29tEGMVRGo211fpBXEidBny7Mk7rQRckVilS/dAySo08N2+fI0hxqOFSsvIlewZwVsvIhc+cCLpG56L0ZgxaaOcK2kXjomL3sjmUESXl5MXhfM7cYftxh5WVDNqwkvO/1X9ZBzRWLghcyKWb5EBFYEG00vC8q56VGs68V2BF+Er+dlgTScKsDf6tURzqgsN5KZhhdiK57MXo18iWCNNfq+QSNfOgBkYZzYqnuhyxWJspcYgL4pwY8V6yh8hTldI4aX1tFWQfuAvIKObGCnkJPhhjRXJCJf5qVvEUOtEiuyjsprNZwhjuCLEJ8A7yWRbGFPHcWZ8moVFWRyg65LGJXkS1yhFc/fl+SLyJWkmlDue4mRHy+VMb7rRfNmywrhpSiSFVRsJfVSWEfPleWKJCq6vqwMx7ZWjGFe4KUOVVoprCNhJaoyjAyRL7lVXbWVNF9unz+tEObljRjn3ictqrin/EJ0mxgr8mbEQsY5bYHWjyyMuPHi0Eqel4UTK+Iqv77yMnRVQUe+ellWNP64pf05X2ouc0XSPXz2gvXw3ITmJV9qELu1Is7SJy9oD/GNaM4zL8O0gdIxFy8DokZRVRpHL6gdOeac6qjq8cctso784DGsiLN0kNPY2E1/JjRlAwDp1JcObVi18FtETei+wxvWw24ERlQN6Ho8NdsD25YrRPoAnZB8Lq6UQC4k68DmQbyki6HiQ+g4DGFFjhiFF9eRpByXiC3hFaknzZDMivTyCNeX08I5x16SOZxmFx6hjhbn8Yfw4i57OwD1T3/YuM3cq1GZw3zpwKF+9UewaYy2Zno1Vl3CzE00HZh9/QuXXqYwuJpeXlqvMTCic3uz4tJL7aYx24mX3E7oujMvcn3qV6r30pzkf/AEbrw09zlW0tVulXppz4tu9514eYKCpQ3VehGD5rjoJqVVvRfxlnm5ImlW6KW5vveMrPJ8CbJFxLlUly/tkieHQbVPoUt+cfHPURW33+fp23uRFCU1PqXpcNy9gJrFobznN6jOS7+8SAovyIjkPGLNIRhUNLmbqFw66LNXzYonHwVUkS9KVjw5MCCto0i9j7NWQUUnsFF8vDulrKPCZp/8SKjrKIFX5c+YPd1ZivQas6kfqSVaUypUddR9UWjIvULUEWELQ6I5HSjqiGDCzp/Bu+5zhildE0N7DW+av+WeYMcrf2OytIGsuaOxNpiUxPcSGna3Yixyz0HkSsdgqnaK7EVrIdEVJI1j7YPS/nm3LFC92HRCE3hpvBtawd1psL+16Q/vY9eRca5I8HYaNFwCfQY5X/JaTTUYIUVjayX1gjcxZWkFq47qCMtk+3gTU9ZWcBpgLDcpyUDz8lHQ3K+F/Z6HWP3hoo4wll6Nixfs6GC7M2WE1t3a3SLky72FQ1r0YxsvqJ3Q9k2hRuOPAix21EPuhB5Y1tEGp4IyjNsxJzDA7Q+3qiN/i7w4yLDRm2BjWJs60txoQgGjX5Cka34AkzQBe9ofs1rbTCgi6ug4M71XrYrWkKbnN7uIR7qXcvxckZwunqoXPbrNr49XCE0tpltBlZKdJcWjU/aH92QkelrIrKTTZIGqlj7pMlm53PRDR4vZ9liKpLfxSlqovxRiAfMXDS32m1jeRQ76lLQQfrVKtyGQ9/DqWrrUq+vEcE1JC90X8cjb9wwNLWS5EtSmgt1BbRhLuGSqef7WJuUnX126haHBriNJko6LBl6GYRiGYRiGYRiGYRiGwWDpdA+Bh+WP311H8JB8Yy15sJZcvv9wHcEVP6OF4E+H2476keC3X34dix8Pc939eXwS9Z+7CBr/np+HwT/uwrjGH7UEI/JvMLkXQhiG3t8/PN8Pne8M9Wh850tuHvxJlMu3x/okehTgL9cRPCRtx/vNEfI/XxBP8EMqRaoAAAAASUVORK5CYII="
alt="A positive and neative crossing"><br>
<div style="text-align: left;"><br>
There exists different ways to describe a knot diagram: Planar Diagram,
Gauss Code, Dowker Notation, Conway Notation.</div>
</div>
</td>
</tr>
<tr>
<td
style="vertical-align: top; background-color: rgb(255, 255, 255);">An
other way to describe a knot is to use quandles. From a knot K, we can
construct the knot quandle Q(K), whose generators are the arcs of K,
and relations are associated to the crossings:<br>
<br>
<div style="text-align: center;"><img alt="Relators knot quandles"
src="Images/a_b_c_neg.png"><br>
This figure gives us "a ▹ b = c" at a negative crossing, and "a ▹-1
b = c" (or "c ▹ b = a") at a positive one.
</
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 204);">gap>
K:=PureCubicalKnot(3,1);;<
br>
gap> G:=GaussCodeOfPureCubicalKnot(K);;<
br>
gap> P:=PresentationKnotQuandle(G);<
br>
rec( generators := [ 1 .. 3 ], relators := [ [ [ 3, 2 ], 1 ], [ [ 1, 3
], 2 ], [ [ 2, 1 ], 3 ] ] )</
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 255);">From
this
example,
we
see
that the generators of the Trefoil Knot Quandle
are the arcs 1, 2 and 3; these generators satisfy the relations above.<
br>
<
br>
<u>Nb</u>: [[a<
sub>1</
sub> ,a<
sub>2</
sub> ],a<
sub>3</
sub> ] means
a<
sub>1</
sub> ▹ a<
sub>2</
sub> = a<
sub>3</
sub>, no matter if we consider
a positive or negative crossing.</
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 255);">We
can also easily go from a Planar Diagram representation of a knot to a
its Gauss
Code (with orientations of crossings).</
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 204);">gap>
PD:=PlanarDiagramKnot(3,1);<
br>
[ [ 1, 4, 2, 5 ], [ 3, 6, 4, 1 ], [ 5, 2, 6, 3 ] ]<
br>
gap> G:=PD2GC(PD);<
br>
[ [ [ -1, 3, -2, 1, -3, 2 ] ], [ -1, -1, -1 ] ] </
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 255);">Using
quandles,
we
can
construct
an knot invariant: a list made of the number
of Homomorphisms beetween the knot (in the
form of a record) and a
connected quandle.</
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 204);">gap>
K:=PresentationKnotQuandleKnot(8,2);<
br>
rec( generators := [ 1 .. 8 ], relators := [ [ [ 8, 2 ], 1 ], [ [ 2, 5
], 1 ], [ [ 2, 6 ], 3 ], [ [ 3, 7 ], 4 ], [ [ 4, 8 ], 5 ],<
br>
[ [ 6, 1 ], 5 ], [ [ 6, 3 ], 7 ], [ [ 7, 4 ], 8 ] ] )<
br>
gap> Q:=ConnectedQuandle(9,2);;<
br>
gap> NumberOfHomomorphisms(K,Q);
time;<
br>
9<
br>
</
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 255);">The
following
code shows how the humber of quandle homomorphisms K--->Q
from a knot quandle K to a finite quandle Q can be used to distinguish
between knots. The
code establishes that by using only connected finite
quandles Q of order <=13 one can distinguish between all prime knots
on at most eight crossings. <
br>
</
td>
</
tr>
<
tr>
<
td
style=
"vertical-align: top; background-color: rgb(255, 255, 204);">gap>
L:=[];;
#List of prime knots on <= 8 crossings<
br>
gap> for n in [1..8] do<
br>
> for i in [1..NumberOfPrimeKnots(n)] do<
br>
> Add(L,PresentationKnotQuandleKnot(n,i));<
br>
> od;od;<
br>
<
br>
gap> inv:=function(K,n); #A knot invariant<
br>
> return List(ConnectedQuandles(n),x->NumberOfHomomorphisms(K,x));<
br>
> end;;<
br>
gap> C:=Classify(L,K->inv(K,3));;<
br>
gap> List(C,Size);<
br>
[ 11, 23, 1 ]<
br>
gap> C4:=RefineClassification(C,K->inv(K,4));;<
br>
gap> List(C4,Size);<
br>
[ 8, 3, 6, 17, 1 ]<
br>
gap> <
br>
gap> C5:=RefineClassification(C4,K->inv(K,5));;<
br>
gap> List(C5,Size);<
br>
[ 5, 2, 1, 1, 1, 1, 1, 1, 4, 3, 12, 1, 1, 1 ]<
br>
gap> C6:=RefineClassification(C5,K->inv(K,6));;<
br>
gap> List(C6,Size);<
br>
[ 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 4, 3, 12, 1, 1, 1 ]<
br>
gap> C7:=RefineClassification(C6,K->inv(K,7));;<
br>
gap> List(C7,Size);<
br>
[ 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 2, 8, 2, 1, 1, 1 ]<
br>
gap> C8:=RefineClassification(C7,K->inv(K,8));;<
br>
gap> List(C8,Size);<
br>
[ 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 6, 2, 2, 1, 1, 1 ]<
br>
gap> C9:=RefineClassification(C8,K->inv(K,9));;<
br>
gap> List(C9,Size);<
br>
[ 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 3, 2, 1,
1, 1, 1, 1, 1, 1 ]<
br>
gap> C10:=RefineClassification(C9,K->inv(K,10));;<
br>
gap> List(C10,Size);<
br>
[ 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 3, 2, 1,
1, 1, 1, 1, 1, 1 ]<
br>
gap> C11:=RefineClassification(C10,K->inv(K,11));;<
br>
gap> List(C11,Size);<
br>
[ 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1 ]<
br>
gap> List(C12,Size);<
br>
[ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ]<
br>
gap> C13:=RefineClassification(C12,K->inv(K,13));;<
br>
gap> List(C13,Size);<
br>
[ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ]<
br>
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