On 1 January 2014 12:51, Jean-Pierre Flori <[email protected]> wrote:
>
>
> On Wednesday, January 1, 2014 5:30:09 AM UTC+1, john_perry_usm wrote:
>>
>> I sometimes illustrate techniques of polynomial factorization in a class
>> by starting with a polynomial in ZZ[x] and converting it to a polynomial in
>> GF(insert_large_prime)[x]. I realize this is not an instance of two _finite_
>> fields, but (a) you mention "the characteristics are different", and (b)
>> _are_ there similar applications for finite fields, when the characteristics
>> are different?

This seems absolutely fine to me since there is a natural ring
homomorphism in that case (which is why it is useful for
factorization!).  What I don't like is this:

sage: GF(7)(ZZ(GF(11)(7)))
0

where the convenient lifting function from GF(p) to ZZ is done
automatically instead of via the functions lift() and centerlift()
which give different answers of course:

sage: GF(7)((GF(11)(7)).lift())
0
sage: GF(7)((GF(11)(7)).centerlift())
3

John


>
> I was rather thinking about positive characteristic, let's leave zero alone
> :)
>
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