Brett Frankel
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 Jan 5 awarded Yearling Jun 1 awarded Necromancer Feb 11 revised How would you go about proving that any complex line is a curve on the Riemann sphere? Removed Riemannian geometry tag Jan 18 asked Semisimplicity of Frobenius action on H^1(X,Q_p) Jan 5 awarded Yearling Nov 30 comment Compositum of all Galois extensions of prime power degree It's an isomorphism. Nov 29 comment Compositum of all Galois extensions of prime power degree @AngeloRendina By $E_i$, do you mean what I called $K_i$? If so, automorphisms of the $E_i$ are not subgroups but quotient groups. So it should be correct as I originally wrote it. Nov 27 revised Compositum of all Galois extensions of prime power degree added 17 characters in body Nov 27 revised Compositum of all Galois extensions of prime power degree added 664 characters in body Nov 27 comment Compositum of all Galois extensions of prime power degree Yes, there's some work to be done here, but the fact that the subextensions are Galois means it will work out. Give me a few minutes and I'll sketch out something more complete. Nov 27 comment Compositum of all Galois extensions of prime power degree Well, what is the compositum? It's the set of elements that can be obtained from elements of these finite extensions. So you just have to show, by induction, that if you take the compositum of two finite Galois extensions of $p$-power order, the compositum is again of $p$-power order (and so is its Galois closure) Nov 27 answered Compositum of all Galois extensions of prime power degree Nov 21 comment Prove that any subfield of $\Bbb R$ contains $\Bbb Q$ Your proof is correct, but could perhaps use some more details (why do you reach each conclusion?) Also, why doesn't your proof work for $\mathbb Z/p$? You must be using some property of $\mathbb R$, but you don't explicitly say what property you are using. Nov 17 comment Why every central simple algebra has a splitting field @Dune The Tensor product of a central simple algebra with a simple algebra is always simple. Nov 17 revised Why every central simple algebra has a splitting field edited tags Nov 9 comment A proposition on Mobius map The only group-theoretic observation, which we can make without using the language of groups, is that given an automorphism $\psi$ with $\psi(a)=0$ for some $a$, we can write $\psi=\tau \circ \varphi_a$, where $\tau$ maps $0$ to $0$. Nov 8 answered A proposition on Mobius map Oct 21 revised product considering the period of index over a cyclotomic extension added 31 characters in body; edited title Oct 7 awarded Nice Answer Sep 30 reviewed Looks OK Thinking about a probability problem in terms of sets.