Resolution
Global GMS
ES Strata
Build. Blocks
Comb. Appl.
HCA Proving
Arrangements
Branches
Classify
Coding
Deformations
Equidim Part
Existence
Finite Groups
Flatness
Genus
Hilbert Series
Membership
Nonnormal Locus
Normalization
Primdec
Puiseux
Plane Curves
Saturation
Solving
Space Curves
Spectrum
Singularities of plane curves - An Example

ring s = 0,(x,y),ds;
poly f = y2-2x28y-4x21y17+4x14y33-8x7y49+x56+20y65+4x49y16;
LIB "sing.lib";
LIB "classify.lib";
classify(f);
==> The singularity is R-equivalent to A[2260]: y2+x2261
Milnor number(f) = 2260
modality(f) = 0
ring r = 0,(x,y),dp;
poly f = fetch(s,f);
tjurina(f);
==> 2260
Hence, Tglobal(f) = Tlocal(f) (= local Milnor number for Ak-sing.). ring sh = 0,(x,y,z),dp;
poly f = fetch(s,f);
poly F = homog(f,z); // homogeneous polynomial defining C
ring r1 = 0,(y,z),dp;
map phi = sh,1,y,z;
poly g = phi(F); // F in affine chart (x=1)
tjurina(g);
==> 120

ring r2 = 0,(y,z),ds; // local ring at (1:0:0)
poly g = fetch(r1,g);
tjurina(g);
==> 120
We conclude: there is (precisely) 1 singularity of C at infinity.
(We have considered all points at infinity except (0:1:0) which is obviously not on C.) Topological type of the singularity at (1:0:0) : x9-y16 = 0.


KL, 06/03 http://www.singular.uni-kl.de