View source for 06-1350/Syzygies in Asymptote in Brief

===Installation===
See [[06-1350/Syzygies in Asymptote]] for more detailed information.

First install [http://asymptote.sourceforge.net Asymptote].  Once installed, download [http://www.math.utoronto.ca/~andy/syzygy.asy syzygy.asy].

===Braids===
{|align=center cellpadding="5"
|-
|<pre>
import syzygy;  // Accesses the syzygy module.
Braid b;        // Start a new braid.
b.n=3;          // The braid has three strands.
                // The strands are numbered left to right starting at 0.
b.add(bp,0);    // Add a overcrossing component starting at strand 0,
                // the leftmost strand.
b.add(bm,1);    // Add an undercrossing starting at strand 1.
b.add(phi,0);   // Add a trivalent vertex that merges strands 0 and 1.
                // Strand 2 is now renumbered as strand 1.
b.draw();       // Draw the resulting braid.
</pre>
|[[Image:06-1350-mybraid.png]]
|}

===Relations===
{|align=center cellpadding="5"
|-
|<pre>
import syzygy;      // Access the syzygy module.
Braid l;            // Define the left hand side of the relation.
l.n=3;  l.add(bp,0);  l.add(bp,1);  l.add(bp,0);
Braid r;            // Define the right hand side of the relation.
r.n=3;  r.add(bp,1);  r.add(bp,0);  r.add(bp,1);

Relation r3;        // Define a relation.
r3.lsym="\rho_3";   // Give the relation a formula name.
r3.codename="rho3"; // Give the relation a name to be used by Mathematica.
r3.lhs=l;  r3.rhs=r;
r3.draw();
</pre>
|[[Image:06-1350-R3-asy.png]]
|}

<code>r3.toFormula()</code> produces the formula:

<math>
(1230)^\star B^+ (1213)^\star B^+ (1023)^\star B^+ = 
(1123)^\star B^+ (1203)^\star B^+ (1231)^\star B^+
</math>

<code>r3.toLinear()</code> produces the formula in linear form:

<math>
\rho_3(x_1,x_2,x_3,x_4) = b^+(x_1,x_2,x_3) + b^+(x_1+x_3,x_2,x_4) + b^+(x_1,x_3,x_4) - b^+(x_1+x_2,x_3,x_4) - b^+(x_1,x_2,x_4) - b^+(x_1+x_4,x_2,x_3)
</math>

and <code>r3.toCode()</code> produces a version usable in Mathematica:

<pre>
rho3[x1_, x2_, x3_, x4_] :> bp[x1, x2, x3] + bp[x1 + x3, x2, x4] + bp[x1, x3, x4]
                            - bp[x1 + x2, x3, x4] - bp[x1, x2, x4] - bp[x1 + x4, x2, x3]
</pre>

===Syzygies===

{|align=center cellpadding="5"
|-
|<pre>
import syzygy;

// Phi around B
Braid initial;
initial.n=4;
initial.add(bp,2);
initial.add(bp,0);
initial.add(bp,1);
initial.add(bp,0);
initial.add(bp,2);
initial.add(phi,1);

Syzygy pb;
pb.lsym="\Phi B";
pb.codename="PhiAroundB";
pb.initial=initial;
pb.apply(r3,1,0);
pb.apply(r4a,3,1);
pb.swap(2,3);
pb.apply(r4b,0,1);
pb.apply(-r3,1,0);
pb.apply(-r4a,0,0);
pb.swap(2,3);
pb.apply(-r4b,3,0);
pb.apply(r3,1,1);

pb.draw();
</pre>
|[[Image:06-1350-bpsmall.png]]
|}

Again, like relations, we can use <code>pb.toLinear()</code>

{| align=center
|-
|<math>\Phi B(x_1,x_2,x_3,x_4,x_5) = </math>
|<math>\rho_3(x_1,x_2,x_3,x_5) + \rho_{4a}(x_1+x_5,x_2,x_3,x_4) + \rho_{4b}(x_1+x_2,x_3,x_4,x_5)</math>
|-
|
|<math>- \rho_3(x_1,x_2,x_3+x_4,x_5) - \rho_{4a}(x_1,x_2,x_3,x_4)</math>
|-
|
|<math>- \rho_{4b}(x_1,x_3,x_4,x_5) + \rho_3(x_1+x_3,x_2,x_4,x_5).</math>
|}

and <code>pb.toCode()</code>

<pre>
PhiAroundB[x1_, x2_, x3_, x4_, x5_] :> rho3[x1, x2, x3, x5] + rho4a[x1 + x5, x2, x3, x4]
 + rho4b[x1 + x2, x3, x4, x5] - rho3[x1, x2, x3 + x4, x5] - rho4a[x1, x2, x3, x4]
 - rho4b[x1, x3, x4, x5] + rho3[x1 + x3, x2, x4, x5]
</pre>

to produce formulas.