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D.6.14.8 posweight
Procedure from library spcurve.lib (see spcurve_lib).
- Usage:
- posweight(M,t1,n[,s]); M matrix, t1 module, n int, s string
n=0 : all deformations of non-negative weight
n=1 : only non-constant deformations of non-negative weight
n=2 : all deformations of positive weight
- Assume:
- M is a presentation matrix of a Cohen-Macaulay codimension 2
ideal and t1 is its T1 space in matrix notation
- Return:
- new ring containing a list posw, consisting of a presentation
matrix describing the deformation given by the generators of T1
of non-negative/positive weight and the weight vector for the new
variables
- Note:
- The current basering should not contain any variables named
T(i) where i is some integer!
Example:
| | LIB "spcurve.lib";
ring r=32003,(x(1),x(2),x(3)),ds;
ideal curve=(x(3)-x(1)^2)*x(3),(x(3)-x(1)^2)*x(2),x(2)^2-x(1)^7*x(3);
matrix M=isCMcod2(curve);
list l=matrixT1(M,3);
def rneu=posweight(l[1],std(l[2]),0);
setring rneu;
pmat(posw[1]);
==> T(2)+x(1)*T(1), -x(3)+x(1)^2,
==> -x(3), x(2),
==> x(2), -x(1)^7
posw[2];
==> 3,1
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