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Prime numbers, diophantine equations, diophantine approximations, analytic or algebraic number theory, arithmetic geometry, Galois theory, transcendental number theory, continued fractions

3 votes

Moduli interpretation for modular curve

By "norm 1 element", you mean "determinant 1 element", right? I guess also that your embedding $K \to M_2(\mathbf{Q})$ is chosen to send $O_K$ into $M_2(\mathbf{Z})$. Then $\Gamma$ is visibly a subgr …
David Loeffler's user avatar
2 votes

Lower bounds for Petersson inner products of cuspforms with integral Fourier coefficients

I typed a comment but the formatting wouldn't come out right, so here it is as an answer! I cannot work out why you expect the "Plancherel or Parseval type" formula to work. Does it not bother you a …
David Loeffler's user avatar
9 votes
Accepted

Chebotarëv data over number fields

I think this is false for cardinality reasons. Take some exceedingly thin, but infinite, set of primes P. Then you can take any valid Chebotarev datum and change it arbitrarily at each prime in P, and …
David Loeffler's user avatar
1 vote

Mod p theta correspondence

I believe Sug Woo Shin has done some work on a mod p theta correspondence; he has given a few talks with that title. I don't know if he's written anything up for public distribution though.
David Loeffler's user avatar
7 votes
Accepted

Mazur-Tate-Teitelbaum p-adic L-function

In order to get $\mathbb{C}_p$-valued functions, you need to choose a basis for the vector space $V_f$. If $f$ corresponds to an elliptic curve, there is a reasonably canonical way of doing this (usin …
David Loeffler's user avatar
11 votes
Accepted

sums modulo p^2

This follows from well-known results (although perhaps not in a totally straightforward way). Let us write $x(a) = a^{-1} + p y(a)$, where $a^{-1}$ denotes the inverse of $a$ modulo $p^2$, and $y(a) …
David Loeffler's user avatar
3 votes
Accepted

Shapiro lemma for Bloch Kato Selmer group

This is a nice exercise. You start by making some reduction steps. Firstly, the BK Selmer group for $T$ is by definition saturated (i.e. it is the preimage in $H^1(K, T)$ of a $\mathbf{Q}_p$-subspace …
David Loeffler's user avatar
4 votes

Is Gauss sum a p-adic measure?

No. The Gauss sum is not a $p$-adic measure. One cheap way to see this is as follows: if $\chi$ has conductor $p^n$, the $p$-adic valuation of $G(\chi)$ is $n/2$. But if $\mu$ is a measure, the asympt …
David Loeffler's user avatar
12 votes
Accepted

Units in quaternionic algebras

If $H$ is definite, then the group of units of $H$ is finite. If $H$ is indefinite, then the group of units is a pretty chunky group; it embeds as a cocompact discrete subgroup of $SL(2, R)$, and the …
David Loeffler's user avatar
9 votes

Bloch-Kato's dual exponential map in a simple setting

As Francois has very clearly explained, the Bloch--Kato dual exponential for $\mathbf{Q}_p(1)$ is indeed zero. Just as a footnote, let me say a few words about how one can "get at" the one-dimensional …
David Loeffler's user avatar
10 votes
0 answers
409 views

Variant of Leopoldt's conjecture

Let $K$ be a number field with $[K : \mathbf{Q}] = d$, and let $p$ be a prime. Let $\sigma_1, \dots, \sigma_d$ be the embeddings of $K$ into $\mathbf{C}_p$. Let $u_1, \dots, u_k$ be a basis of $\mathc …
David Loeffler's user avatar
19 votes
Accepted

semisimplicity of p-adic Galois representations

This can't possibly work. Many p-adic Galois representations are not semisimple. For instance, $\mathbb{Z}_p$ occurs as a quotient of the Galois group of $\mathbb{Q}$ (as the Galois group of the cyclo …
David Loeffler's user avatar
3 votes

Galois representations along eigenvarieties

Are you familiar with the paper "Overconvergent Eichler--Shimura isomorphisms" by Andreatta--Iovita--Stevens? In section 3 of this paper they give a variant of the "modular symbol" construction of the …
David Loeffler's user avatar
19 votes
Accepted

Example of unramified abelian extension

You are slipping up because $i$ does not generate the ring of integers of $L$ as an $\mathcal{O}_K$-algebra: we have $\mathcal{O}_K = \mathbb{Z}[\sqrt{-5}]$, but $\mathcal{O}_L = \mathbb{Z}\left[i, \f …
David Loeffler's user avatar
3 votes

Is it possible to write identity for $ \{x(y^2-z^2)-y\}.\{u(v^2-w^2)-v)\}=a(b^2-c^2)-b$?

Your question strongly suggests that you are trying to understand the set of integers that can be expressed as $a(b^2 - c^2) - b$. But this is rather easy: any integer has this form. Given any $N$, ju …
David Loeffler's user avatar

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