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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

How to compute modular forms of weight one on Shimura curves?

I wonder whether you mean something else, but if you want to know what the answer is (dimensions of spaces, Hecke action etc) then all of this can be read off from Jacquet-Langlands and the analogous …
Kevin Buzzard's user avatar
7 votes

An inequality for the Euler totient function

No it's not true. An equivalent question is whether the product of $(1-1/p)$, where $p$ ranges over all the primes for which 2 has odd order mod $p$, is greater than or equal to $1/2$. However an expl …
Kevin Buzzard's user avatar
5 votes
Accepted

Conditions of solution

As Gerhard says, $m=1$ works giving $p=5$ and $k=3$. I claim that this is the only time it happens. Let $m\geq2$ be an integer, and set $p=2^{2m+1}-2^{m+1}+1$. I don't care if $p$ is prime or not, bu …
Kevin Buzzard's user avatar
5 votes
Accepted

Proof in Schemmel's Paper

The case $n=4$ and $m=35$ given in both the question and the original German paper (link now removed from question) is a little misleading. In this case the sets are disjoint. The case $n=2$ and $m=35 …
Kevin Buzzard's user avatar
2 votes
Accepted

A question about numbers

No. How about $a=9$ and $b=16$? Then $c=25$ so $\Omega(a)=\Omega(c)=2\leq\Omega(b)$, the gcd's are $3,16,5$ so the left hand side is 6 and the right hand side only 5. Edit: if $a=316$ and $b=27$ then …
Kevin Buzzard's user avatar
1 vote

Complete discrete valuation rings with residue field ℤ/p

Greg notes that $(Z/pZ)[[x]]$ is a limit of the integers of a sequence of totally ramified extensions of $Q_p$. At the back of my mind I wonder whether he'd be interested by the Fontaine-Wintenberger …
Kevin Buzzard's user avatar
9 votes
Accepted

Density results for equality of Galois/automorphic representations

Firstly, at the beginning of the question you are missing irreducibility/cuspidality assumptions. If $\rho_1$ and $\rho_2$ are $\ell$-adic Galois reps with the same char poly in a set of primes of den …
Kevin Buzzard's user avatar
14 votes

What is the limit of gcd(1! + 2! + ... + (n-1)! , n!) ?

Here's my guess: it might be out of reach to prove that $g_n$ tends to infinity, but it probably does, because $1!+2!+\ldots+(p-1)!$ is a "random" number mod $p$, so the chances that it's divisible by …
Kevin Buzzard's user avatar
13 votes

Katz Modular Functions and Emerton's Completed Cohomology

I don't think I even know a natural non-zero map from the space $S_2(\Gamma_1(N);\mathbf{Q}_p)$ ("classical" modular forms with $p$-adic coefficients, defined for example as global sections of an appr …
Kevin Buzzard's user avatar
7 votes

A very very good approximation to Ramanujan constant. Why?

This answer pertains to Michael's comment above. Let $c$ be $e^{\pi\sqrt{163}}$. It is well-known that $c$ is close to an integer. More precisely, $c$ is about $10^{-12}$ from an integer of size abou …
Kevin Buzzard's user avatar
10 votes

Reference for Deligne's construction of Galois representations attached to modular forms

I absolutely agree that Deligne is very terse. One thing that I ultimately found very helpful is Carayol's two papers where he proves the analogous theorem for Hilbert modular forms. I say "ultimately …
Kevin Buzzard's user avatar
4 votes
Accepted

How can I evaluate the sum $\sum_{a+b=1;\ a,b \in \mathbb F_p} \left(\frac{a}{p}\right) \chi...

If I've understood the question correctly, this is just a Jacobi sum. The question only seems to make sense for $p$ a prime congruent to 1 mod 3. In this case, the order 3 character and the quadratic …
Kevin Buzzard's user avatar
6 votes

Mid-Square with all bits set

Not an answer, but too long for a comment. I can't see any tricks to do this other than a brute force computational approach. The naive approach would be to loop from $2^{96}$ to $2^{128}$ squaring e …
Kevin Buzzard's user avatar
13 votes
Accepted

Positive polynomial having roots modulo any integer

$\newcommand{\Q}{\mathbf{Q}}\newcommand{\Z}{\mathbf{Z}}$ I now suspect the answer might be no! This isn't a complete answer but it might be an idea that turns into one. So let me assume that such $p$ …
Kevin Buzzard's user avatar
29 votes
Accepted

Complete discrete valuation rings with residue field ℤ/p

Greg, I want to say some basic things, but people are giving quite "high-brow" answers and what I want to say is a bit too big to fit into a comment. So let me leave an "answer" which is not really an …
Kevin Buzzard's user avatar

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