A normal element x in a non-commutative ring R determines an automorphism f of R by a*x=x*f(a). Conversely, given a ring endomorphism, we may ask if any x satisfy the above equation for all a.
i1 : B = skewPolynomialRing(QQ,(-1)_QQ,{x,y,z,w})
Warning: F4 Algorithm not available over current coefficient ring or inhomogeneous ideal.
Converting to Naive algorithm.
o1 = B
o1 : FreeAlgebraQuotient
|
i2 : sigma = map(B,B,{y,z,w,x})
o2 = map (B, B, {y, z, w, x})
o2 : RingMap B <-- B
|
i3 : C = oreExtension(B,sigma,a)
Warning: F4 Algorithm not available over current coefficient ring or inhomogeneous ideal.
Converting to Naive algorithm.
o3 = C
o3 : FreeAlgebraQuotient
|
i4 : sigmaC = map(C,C,{y,z,w,x,a})
o4 = map (C, C, {y, z, w, x, a})
o4 : RingMap C <-- C
|
i5 : normalElements(sigmaC,1)
o5 = | a |
1 1
o5 : Matrix C <-- C
|
i6 : normalElements(sigmaC,2)
o6 = 0
1
o6 : Matrix QQ <-- 0
|
i7 : normalElements(sigmaC * sigmaC,2)
o7 = | a2 |
1 1
o7 : Matrix C <-- C
|
i8 : normalElements(sigmaC * sigmaC * sigmaC, 3)
o8 = | a3 |
1 1
o8 : Matrix C <-- C
|