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D.15.1.17 arrDecone
Procedure from library arr.lib (see arr_lib).
- Usage:
- arrDecone(A, k); arrangement A, integer k;
- Return:
- arr: the deconed hyperplane Arrangement dA
- Note:
- A has to be non-empty and central. arrDecone is an inverse operation
to arrCone since A == arrDecone(arrCone(A),size(A)+1) for any A.
One can also decone a central arrangement with respect to any hyper-
plane k, but than a coordinate change is necessary to make
H_k = ker(x_k). Since such a coordinate change is not unique,
use arrCoordchange to do so.
Example:
| | LIB "arr.lib";
ring R = 0,(x,y,z),dp;
arr A= ideal(x,y,z,x+y-z);
arrDecone(A,3);
==> _[1]=x
==> _[2]=y
==> _[3]=x+y-1
==>
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See also:
arrCone;
arrDecone;
arrEssentialize;
arrIsEssential;
arrRestrict.
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