On Wednesday, August 28, 2024 at 7:57:43 PM UTC+9 john.c...@gmail.com wrote:

Surely the output of -1 for AA(-1)^(1/3) is correct:  AA is the "Algebraic 
Real Field" and -1 has exactly one cube root in there, namely itself.  On 
the other hand, QQbar(-1) has 3 cube roots and one is chosen (in some 
deterministic way).

I do not think that AA(-1)^(1/3) should return a cubroot in another 
field/parent when there is one in the same field/parent.  Compare

sage: QQ(-1).nth_root(3)
-1
sage: RR(-1).nth_root(3)
-1.00000000000000
sage: CC(-1).nth_root(3)
0.500000000000000 + 0.866025403784439*I

which is as it should be (in my opinion!)


x^(1/n) and x.nth_root(n) do not behave in the same way. All x.nth_root(n) 
gives an n-th  root in the same field to which x belongs while all x^(1/n) 
gives the primitive n-th root of unity, with the exception of AA(-1)^(1/n).

 
 

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