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7 votes

How is Taylor-Wiles patching "horizontal Iwasawa theory"?

I think your question already contains its own answer. In classical, "vertical" Iwasawa theory one studies class groups, or other arithetic widgets like elliptic curve Selmer groups, in a limit over $ …
David Loeffler's user avatar
4 votes
Accepted

Integration against Eisenstein series can be regarded as a cup product

Yes, that does indeed sound like something I might have said :) I was referring to some extremely powerful theorems, originally due to Michael Harris, which show that: The cohomology groups of automo …
David Loeffler's user avatar
2 votes

On Kato's proof that Iwasawa Cohomology is free

(1) No, it depends on the maximal ideal (maximal ideals of $\Lambda$ biject with mod $p$ characters of $\Gamma$). (2) no longer makes sense. (3) It would suffice (for this particular step of Kato's pr …
David Loeffler's user avatar
13 votes
Accepted

Do people prefer working on $\mathrm{GSp}$ and $\mathrm{GU}$ rather than $\mathrm{Sp}$ and $...

Symplectic case: Here are two reasons (not necessarily the only ones) why $\operatorname{GSp}_{2n}$ is more convenient to work with than $\operatorname{Sp}_{2n}$. Firstly: there is no Shimura datum w …
David Loeffler's user avatar
6 votes
Accepted

Describing the Gamma-transform explicitly in terms of power series

This is a hard problem (and one which is easily overlooked by the unwary)! Just to be clear, I'll summarize (how I think about) the problem: as a relation between additive and multiplicative Fourier t …
David Loeffler's user avatar
4 votes

Iwasawa theory and perfectoid spaces

A flippant response is that people had the idea of using perfectoid theory in Iwasawa theory long before perfectoid theory even existed. What I'm referring to here is the work of Fontaine--Wintenberge …
David Loeffler's user avatar
5 votes

Completed cohomology and variants

There is no reason why you shouldn't consider completed etale cohomology, instead of completed singular cohomology. If you look at Emerton's 2006 Inventiones paper which started the whole theory, he a …
David Loeffler's user avatar
15 votes
Accepted

Why can Euler systems constructed from algebraic cycles only be anticyclotomic?

Let me explain a bit more what that footnote was supposed to mean. As I'm sure you know, an Euler system for a Galois representation $V$ over a number field $K$ consists of a bunch of classes in $H^1 …
David Loeffler's user avatar
2 votes
Accepted

Adjoint Selmer groups and Deformation rings

As far as I know, it is difficult to extract much information about the adjoint Selmer group over the cyclotomic $\mathbb{Z}_p$-extension. If the modular form $f$ corresponding to $\rho$ is ordinary a …
David Loeffler's user avatar
4 votes
Accepted

Modular symbols associated to Rankin Selberg convolutions and the symmetric square

I do not think there is a reference for this theory, because as far as I know no such theory exists. I have spent a substantial portion of my career studying the arithmetic of the special values of th …
David Loeffler's user avatar
4 votes
Accepted

State of the art on the main conjecture for supersingular elliptic curves/modular forms

Theorem (Xin Wan): If $E$ is an elliptic curve of square-free conductor $N$, and $p \ge 3$ is a prime such that $p \nmid N$ and $a_p(E) = 0$, then Kobayashi's $\pm$ Iwasawa main conjectures are tr …
David Loeffler's user avatar
5 votes
Accepted

What is the current status on the corank conjecture for Selmer groups?

Yes, the corank conjecture is a theorem for elliptic curves over $\mathbb{Q}$. The key to the proof is the following: Theorem (Kato, 2004): For any $E$ and any $p$, the "fine Selmer group" $Sel_p^ …
David Loeffler's user avatar
4 votes

Herbrand-Ribet and Mazur-Wiles for function fields

(I was hoping somebody else would answer this, because function fields are not really my area and I hoped I would learn something from the answer; but nobody seems to be biting, so...) Iwasawa theory …
David Loeffler's user avatar
5 votes
Accepted

Main conjecture for elliptic curves invariant under a $\mathbb{Q}$-isogeny

Yes, the main conjecture is isogeny-invariant. See here: B. Perrin-Riou, Variation de la fonction $L$ $p$-adique par isogénie, Algebraic number theory, Adv. Stud. Pure Math. 17 (1989), pp. 347-358.
David Loeffler's user avatar
10 votes
Accepted

Main conjecture for elliptic curves

The main conjecture is a theorem if the image of the mod $p$ Galois representation of E is the whole of $GL_2(\mathbf{F}_p)$. The full statement of the conjecture, which implies what you wrote about l …
David Loeffler's user avatar

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