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7.7.4.0. charVariety
Procedure from library dmodapp.lib (see dmodapp_lib).

Usage:
charVariety(I [,eng]); I an ideal, eng an optional int

Return:
ring (commutative) containing an ideal 'charVar'

Purpose:
computes an ideal whose zero set is the characteristic variety of I in
the sense of D-module theory

Assume:
The basering is the n-th Weyl algebra over a field of characteristic 0
and for all 1<=i<=n the identity var(i+n)*var(i)=var(i)*var(i+1)+1
holds, i.e. the sequence of variables is given by
x(1),...,x(n),D(1),...,D(n), where D(i) is the differential operator
belonging to x(i).

Note:
The output ring is commutative. It contains an ideal 'charVar'.
If eng<>0, std is used for Groebner basis computations,
otherwise, and by default, slimgb is used.

Display:
If printlevel=1, progress debug messages will be printed,
if printlevel>=2, all the debug messages will be printed.

Example:
 
See also: charInfo.


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