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7.5.3.0. variablesSorted
Procedure from library central.lib (see central_lib).
- Usage:
- variablesSorted();
- Return:
- ideal, generated by sorted algebra variables
- Purpose:
- computes the set of algebra variables sorted so that
Cartan variables go first
- Note:
- This is a heuristics for the computation of the center:
it is better to compute centralizers of Cartan variables first since in this
case we can omit solving the system of equations.
Example:
| | LIB "central.lib";
ring AA = 0,(x,y,z),dp;
matrix D[3][3]=0;
D[1,2]=-z; D[1,3]=2*x; D[2,3]=-2*y;
def A = nc_algebra(1,D); setring A; // this algebra is U(sl_2)
// There is only one Cartan variable - z in U(sl_2),
// it must go 1st:
variablesSorted();
==> _[1]=z
==> _[2]=y
==> _[3]=x
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See also:
variablesStandard.
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