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Aug 13, 2015 at 6:50 vote accept Pablo
Aug 6, 2015 at 15:22 comment added Pablo mathoverflow.net/questions/213033/… mathoverflow.net/questions/212906/…
Aug 6, 2015 at 15:20 comment added Pablo @NoamD.Elkies Please note that if we confine ourselves to compistums of quadratic extensions, then by a 1974 result of Frey and Jarden it is not possible for all primes to ramify (they prove that an elliptic curve over the compositum of all quadratic extensions of $\mathbb{Q}$ has infinite rank). In light of that I conjecture that if many primes ramify (say with respect to some density) then all elliptic curves should have rank $\infty$. How big can you make the set primes ramifying here? Some related questions are:
Aug 6, 2015 at 15:06 comment added Noam D. Elkies to Pablo's question: the field will be the compositum of infinitely many quadratic extensions, and thus will have infinitely many ramified prime and a Galois group that's abelian of exponent 2.
Aug 6, 2015 at 14:59 comment added Noam D. Elkies It seems that this kind of construction should even work unconditionally, replacing Tate-Shafarevich by the Heegner construction (for positive rank) and Kolyvagin etc. or even an explicit 2-descent (for rank zero).
Aug 6, 2015 at 14:31 comment added Pablo @YonatanHarpaz This sounds amazing! Can you point out some properties of the arising field like how many rational primes ramify there, or what is the Galois group over $\mathbb{Q}.$
Aug 6, 2015 at 13:17 comment added Lubin Thanks for this. It’s what I would have expected, but what do I know?
Aug 6, 2015 at 13:15 history answered Yonatan Harpaz CC BY-SA 3.0