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Questions about modular forms and related areas

6 votes
Accepted

Overconvergent cohomology and overconvergent modular forms

Unfortunately there isn't a simple direct relationship between OC mod forms and OC cohomology! The miracle is that they contain the same finite-slope Hecke data. As you've guessed, one proves this by …
David Hansen's user avatar
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4 votes
0 answers
131 views

A lower bound for short averages of L-functions

Suppose $f$ is a weight $k$ cuspidal Hecke eigenform on the full modular group, with its L-function $L(s,f)$ normalized such that $s=1/2$ is the central point. Is a bound of the form $\int_{-1}^{1}| …
David Hansen's user avatar
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6 votes
Accepted

Lehmer's conjecture for Ramanujan's tau function

One of the canonical references for questions like this is Serre's "Quelques applications du theoreme de densite de Chebotarev", Publ. Math. IHES 54. He proves, for example, that the number of primes …
David Hansen's user avatar
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14 votes
Accepted

Modular forms with prime Fourier coefficients zero

Write $f=\sum c_i f_i$ as a sum over new eigenforms. Your condition is thus equivalent to $\sum c_i \lambda_i(p)=0$ for all $p$. Taking the absolute value squared of this and summing over $p\leq X$ …
David Hansen's user avatar
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5 votes
1 answer
517 views

Jacobi's theta function over totally real fields

Suppose $F/\mathbb{Q}$ is a totally real field of degree $d$ and class number one. Fix an ordering $\sigma_1, \dots, \sigma_d$ on the embeddings of $F$. Is $\sum_{\alpha \in \mathcal{O}_F}e^{2\pi i …
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4 votes
Accepted

Tunnel like theorem: is there an interesting function with fourier coefficients related to $...

Yes. Bruinier and Ono have shown in their paper "Heegner divisors, L-functions and harmonic weak Maass forms" that the vanishing or nonvanishing of central derivatives of twisted L-functions like thi …
David Hansen's user avatar
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4 votes
0 answers
132 views

Uniform distribution of special homology classes mod-p

Let $X_0(N)$ be the usual modular curve. For $\chi$ a quadratic Dirichlet character of conductor $D$, define the homology class $c(\chi)=\sum_{i=0}^{|D|-1}\chi(i)\{\frac{i}{|D|}{\infty} \}$; here $\{ …
David Hansen's user avatar
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0 votes

Functions on hyperbolic space and modular curves

The infinite-dimensional unitary representations of $SL_{2}\left(\mathbb{R}\right)$ appearing in the right-regular representation on $L^{2}\left(H\right)$ are precisely the unitary representations of …
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0 votes

Why are powers of $\exp(\pi\sqrt{163})$ almost integers?

I think the right approach would be to observe that $R^n$ is the leading term in $j(n\tau)$ as above. Then there is a modular polynomial $\Phi_n$ which satisfies $\Phi_n(j(x),j(nx))=0$. For small $n …
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17 votes
1 answer
812 views

The graph of congruences between modular forms

Let $S$ be the (countable) set of holomorphic cuspidal new eigenforms of weight $\geq 2$. Any $f\in S$ has a level $N_f$ and a canonically normalized Fourier expansion $f(z)=\sum_{n=1}^{\infty}a_f(n)e …
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10 votes
1 answer
671 views

Level raising by prime powers

Suppose $f$ is a weight $2$ level $N$ cusp form. When can we realize the mod-$\ell$ representation of $f$ in a form of weight $2$ and level $Np^3$, where $p$ is some prime not dividing $N$? I assume …
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22 votes
1 answer
3k views

The difficulties in proving modularity lifting theorems over non-totally real fields

First of all, let me apologize in advance for the terseness of this question. It seems that by now there are well-developed techniques (the "Taylor-Wiles-Kisin" method) for proving modularity lifting …
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9 votes
1 answer
640 views

Galois orbits of newforms with prime power level

Let me start with a simple observation. Suppose $f$ is a weight two newform of level $p^3$. Write $d$ for the size of the Galois orbit $f^\sigma, \sigma \in \mathrm{Gal}(\overline{\mathbf{Q}}/\mathb …
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7 votes
0 answers
490 views

"Nontrivial" singular points on the eigencurve?

Let $\mathscr{C}$ be the Coleman-Mazur-Buzzard eigencurve of some fixed tame level $N$. Are there any known examples of a singular point $x\in \mathscr{C}$ which lies in a unique irreducible componen …
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6 votes
2 answers
842 views

Serre's conjecture for mod-p^n representations?

I think this may be a silly question, but here goes. Let $\rho:\mathrm{Gal}(\overline{\mathbf{Q}}/\mathbf{Q})\to \mathrm{GL}_2(\overline{\mathbf{F}_p})$ be a representation; say $\rho$ is of S-type i …
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