Splitting Fields


by hypermonkey2
Tags: fields, splitting
hypermonkey2
hypermonkey2 is offline
#1
Feb18-09, 08:31 PM
P: 102
I was thinking about this,
finding the splitting field of x^4-2 in Q[x] over Q is standard enough... but would much be different is i wanted the splitting field over F_5? (field with 5 elements)
would it just be F_5(2^(1/4), i) analogously to the Q case? or do any of the arguments break down?

Any thoughts are appreciated,
cheers
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Citan Uzuki
Citan Uzuki is offline
#2
Feb18-09, 10:21 PM
PF Gold
P: 274
I think it would be just F_5(2^(1/4)), since once you have one fourth root of 2, the others would just be 2*2^(1/4), 4*2^(1/4), and 3*2^(1/4) (since 2^4 = 1 in F_5).
hypermonkey2
hypermonkey2 is offline
#3
Feb18-09, 10:36 PM
P: 102
Quote Quote by Citan Uzuki View Post
I think it would be just F_5(2^(1/4)), since once you have one fourth root of 2, the others would just be 2*2^(1/4), 4*2^(1/4), and 3*2^(1/4) (since 2^4 = 1 in F_5).

Very true! However, what does 2^(1/4) mean exactly in this case? i dont think it can be a real number since i dont believe there is an extension from F_5 to R...
And since there is no element x in F_5 such that x^4=2...

perhaps i am confused?

Thanks for you reply!

Citan Uzuki
Citan Uzuki is offline
#4
Feb18-09, 11:11 PM
PF Gold
P: 274

Splitting Fields


No, it wouldn't be an element of R. It would be an element of some algebraic extension of F_5. In this case, since the polynomial x^4 - 2 is irreducible over F_5, we can take that extension to be the quotient ring F_5[X]/(X^4 - 2).


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