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Reduction mod p of a polynomial

asked 1 year ago

tungnt gravatar image

Hi everyone,

I have a question about the factorization of a polynomial modulo a prime ideal that I would like to help with.

Specifically, let K be a number field (for my problem, we can assume that K=Q[i] or K=Q[ω]). I have a polynomial f in OK[x] and a prime ideal p in OK and I want to compute the factorization of f over OK/p.

When K=Q, I use the following built-in function.

f=f.change_ring(GF(p))
f.factor()

I wonder whether we can do the same for a general number field.

Thank you for your help.

-Tung

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answered 1 year ago

tungnt gravatar image

My collaborator finally figured out how to do this. For your interest, here is how we do it. Let K be the number field, P the prime ideal, and f the polynomial that we want to factor modulo P.

G = K.factor(P)[0][0].residue_field()
f.change_ring(G).factor()

Hope this helps if someone arrives at the same problem in the future.

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slelievre gravatar imageslelievre ( 1 year ago )

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Asked: 1 year ago

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Last updated: Aug 21 '23