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D.6.6.3 esStratum

Procedure from library equising.lib (see equising_lib).

Usage:
esStratum(F[,m,L]); F poly, m int, L list

Assume:
F defines a deformation of a reduced bivariate polynomial f and the characteristic of the basering does not divide mult(f).
If nv is the number of variables of the basering, then the first nv-2 variables are the deformation parameters.
If the basering is a qring, ideal(basering) must only depend on the deformation parameters.

Compute:
equations for the stratum of equisingular deformations with fixed (trivial) section.

Return:
list l: either consisting of a list and an integer, where
 
  l[1][1]=ideal defining the equisingularity stratum
  l[1][2]=ideal defining the part of the equisingularity stratum where all
          equimultiple sections through the non-nodes of the reduced total
          transform are trivial sections
  l[2]=1 if some error has occured,  l[2]=0 otherwise;
or consisting of a ring and an integer, where
 
  l[1]=ESSring is a ring extension of basering containing the ideal ES
        (describing the ES-stratum), the ideal ES_all_triv (describing the
        part with trival equimultiple sections) and the polynomial p_F=F,
  l[2]=1 if some error has occured,  l[2]=0 otherwise.

Note:
L is supposed to be the output of hnexpansion (with the given ordering of the variables appearing in f).
If m is given, the ES Stratum over A/maxideal(m) is computed.
This procedure uses execute or calls a procedure using execute. printlevel>=2 displays additional information.

Example:
 
See also: esIdeal; isEquising.


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