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D.6.9.12 delta
Procedure from library hnoether.lib (see hnoether_lib).
- Usage:
- delta(INPUT); INPUT a polynomial defining an isolated plane curve
singularity at 0, or the Hamburger-Noether expansion thereof, i.e.
the output of
develop(f) , or the output of hnexpansion(f) ,
or the list of HN data computed by hnexpansion(f) .
- Return:
- int, the delta invariant of the singularity at 0, that is, the vector
space dimension of R~/R, (R~ the normalization of the local ring of
the singularity).
- Note:
- In case the Hamburger-Noether expansion of the curve f is needed
for other purposes as well it is better to calculate this first
with the aid of
hnexpansion and use it as input instead of
the polynomial itself.
Example:
See also:
deltaLoc;
invariants.
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