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

Usage:
charInfo(I); I an ideal

Return:
ring (commut.) containing ideals 'charVar','singLoc' and list 'primDec'

Purpose:
computes characteristic variety of I (in the sense of D-module theory),
its singular locus and primary decomposition

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:
In the output ring, which is commutative:
- the ideal 'charVar' is the characteristic variety char(I),
- the ideal 'SingLoc' is the singular locus of char(I),
- the list 'primDec' is the primary decomposition of char(I).

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

Example:
 


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