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kGonalNodalCurves :: sectionsFromPoints

sectionsFromPoints -- computes matrix defining the canonical embedding from the 2g points

Synopsis

Description

Given the g pairs of points Pi,Qi we can proceed as follows:

Step 1. We compute g quadrics qi :=det(Pi | (x0,x1)t) * det(Qi | (x0,x1)t).

Step 2. We compute a basis of H0(C,ωC) by {si :=∏gj≠i,j=1qi | i=1,...,g } and multiply the matrix s=(s1,...,sg) wih a general matrix M∈GL(g,kk) to obtain more general sections.

i1 : (k,g,n)=(4,8,1000);
i2 : (p,kk,S)=getFieldAndRing(n);
i3 : (P,Q,multL,f)=pickGoodPoints(k,g,n);
i4 : s=sub(sectionsFromPoints(P,Q),S);

             1       8
o4 : Matrix S  <--- S
i5 : T=kk[t_0..t_(g-1)];
i6 : I=ideal mingens ker map(S,T,s);

o6 : Ideal of T
i7 : betti res I

            0  1  2  3  4  5 6
o7 = total: 1 15 39 50 39 15 1
         0: 1  .  .  .  .  . .
         1: . 15 35 25  4  . .
         2: .  .  4 25 35 15 .
         3: .  .  .  .  .  . 1

o7 : BettiTally

See also

Ways to use sectionsFromPoints :

  • sectionsFromPoints(Matrix,Matrix)
  • sectionsFromPoints(Sequence)