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About: About this document inCentralizer
Procedure from library central.lib (see central_lib).

inCentralizer(E, S); E poly/list/ideal, S poly/ideal

integer, 1 if E is in the centralizer(S), 0 otherwise

check whether the elements of E are in the centralizer(S)

LIB "central.lib";
ring R = 0,(x,y,z),dp;
matrix D[3][3]=0;
def r = nc_algebra(1,D); setring r; // the Heisenberg algebra
poly f = x^2;
poly a = z; // 'z' is central => it lies in every centralizer!
poly b = y^2;
inCentralizer(a, f);
==> 1
inCentralizer(b, f);
==> 0
list  l = list(1, a);
inCentralizer(l, f);
==> 1
ideal I = a, b;
inCentralizer(I, f);
==> 0
printlevel = 2;
inCentralizer(a, f); // yes
==> 1
inCentralizer(b, f); // no
==> [1]:
==>    POLY: y2 is NOT in the centralizer of polynomial {x2}
==> 0