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Notes for lecture 2024-09-12

Notes for lecture 2024-09-12

av Benjamin Andersson -
Antal svar: 4

If someone took notes today, I'd be happy if you could send them (I could not attend).

Best,

Ben

Som svar till Benjamin Andersson

Re: Notes for lecture 2024-09-12

av Sofia Tirabassi -
Hello
I uploaded my corrected notes. We did not go over fg+alg implies finite (last page and half)
I added the proof of finite implies finitely generated that was missing (the clever one, not the super long one I created on the spot when I realized I had a gap in my notes) I corrected the the part about iso of simple extensions: we have to require that alpha goes in beta in order to get the same minimal poly. I give an example showeing that this hast to be the case.

MVH
Sofia

P.S>. do not get used to me uploading notes. I will do it just if I feel they are tidy enough :)
Som svar till Sofia Tirabassi

Sv: Re: Notes for lecture 2024-09-12

av Benjamin Andersson -
Thanks. I believe there is a typo in the attached picture, it should be "with p(α) = 0" for the \implies direction.

It seems like you want to say that assuming that α is algebraic then p(α) for some non-zero p(x) in F[x], but then ker eval_α neq 0, so eval_α not injective.
Best,

Ben
Bilaga Skärmbild 2024-09-13 154235.png
Som svar till Benjamin Andersson

Re: Sv: Re: Notes for lecture 2024-09-12

av Sofia Tirabassi -

Yes the two arrows are in the wrong direction. You can also prove the two directions at once eval not injective iff there is a non trivial element p in the kernel, if there is a non zero poly p that vanishes if evaluated at alpha.

Som svar till Benjamin Andersson

Re: Sv: Re: Notes for lecture 2024-09-12

av Sofia Tirabassi -

Yes! You are right. In adfition the two arrows are in the wrong direction.

 You can also prove the two directions at once eval not injective iff there is a non trivial element p in the kernel, if there is a non zero poly p that vanishes if evaluated at alpha.. so this not really a bug deal.


This is exactly the reason I do not usually make my notes public: for a proof like that that I could do I woken up in the middle of the night, I write them down just to estimate the time I will need to present them (I know 2x45 minutes leq 4 pages of notes) without taking care  of them being perfect/correct (as you are starting of discovering with my swapping of Fs and KS I do not always write what my brain means) :)