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D.5.4.7 globalSections
Procedure from library divisors.lib (see divisors_lib).
- Usage:
- globalSections(A); A = divisor.
- Assume:
- A is a divisor on X.
- Return:
- a list with a basis of the space of global sections of D.
- Theory:
- We assume that the qring of X satisfies the S2-condition and that X is smooth. We compute sat((f*J) : I) /f
where D = (I)-(J).
Example:
| | LIB "divisors.lib";
ring r=31991,(x,y,z),dp;
ideal I = y^2*z - x*(x-z)*(x+3*z);
qring Q = std(I);
divisor P = makeDivisor(ideal(x,z),ideal(1));
divisor D = multdivisor(4,P);
globalSections(D);
==> [1]:
==> _[1]=x2
==> _[2]=z2
==> _[3]=yz
==> _[4]=xz
==> [2]:
==> z2
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