# Questions tagged [modular-forms]

Questions about modular forms and related areas

**0**

votes

**0**answers

21 views

### Coset representatives of a principal congruence subgroup by another principal congruence subgroup

Consider the principal congruence subgroup $\Gamma(N)$, this consists of entries in $\mathrm{SL}_2(\mathbb{Z})$ congruent to the identity modulo $N$. Consider another principal congruence subgroup $\...

**6**

votes

**1**answer

536 views

### Galois theory of modular functions

Let $\mathcal M_m$ be the set of $2$-by-$2$ primitive (relatively prime entries) matrices with determinant $m$. Let $\alpha \in \mathcal M_m$ and let $\Gamma\subset \operatorname{SL}_2(\mathbb Z)$. ...

**2**

votes

**0**answers

97 views

### Newman's conjecture of Partition function

(Sorry for my poor english....)
Let $p(n)$ be a partition function and $M$ be an integer. Newman conjectured that for each $0\leq r\leq M-1$, there are infinitely many integers $n$ such that
\begin{...

**3**

votes

**1**answer

191 views

### Why are Poincare series defined as they are?

We know the Poincare series are defined as the following:
The $m^{th}$ Poincare series of weight $k$ for $\Gamma$ is:
$$
P_{m}^{k} (z) = \sum_{(c,d)=1} (cz+d)^{-k} e^{2 \pi in(\tau z)}.
$$
The ...

**1**

vote

**0**answers

66 views

### theta function with a low bound in the sum

I encounter a sum similar to the Jacobi Theta function except there is a lower bound $-J$ with $J\geq 0$:
\begin{equation}
f(q,x)=\sum_{n=-J}^\infty q^{n^2}x^n.
\end{equation}
My question is whether ...

**2**

votes

**0**answers

87 views

### How to express the cuspidal form in terms of Poincare series?

Sorry to disturb. I recently read Blomer's paper. There is a blur which needs the expert's help here. Blomer's paper says "For any cusp form $f$ of integral weight $k$, level $N$, $f$ can be written ...

**3**

votes

**0**answers

109 views

### Is constant map from automorphic form surjective?

Let $G$ be a connected reductive group over $\mathbb{Q}$ and $P=NM$ be a standard parabolic subgroup of $G$ and and $K$ a 'good' maximal compact subgroup of $G$. (For precise definitions of these ...

**3**

votes

**0**answers

97 views

### Automorphy Factor from Vector Bundles on Compact Dual

So I'm coming from an algebraic geometry perspective and I'm trying to carefully piece together the story of interpreting automorphic forms as sections of vector bundles on Shimura varieties. I think ...

**6**

votes

**0**answers

136 views

### Additive and multiplicative convolution deeply related in modular forms

From the fact spaces of modular forms are finite dimensional, from the decomposition in Hecke eigenforms, and from the duplication formula for $\Gamma(s)$ there are a lot of identities mixing additive ...

**2**

votes

**0**answers

81 views

### Deforming Modular Symbols

This is probably a silly question, as I don't really know a whole lot about modular symbols over arbitrary rings.
How do modular symbols over a finite field square with Katz modular forms? If they ...

**6**

votes

**2**answers

334 views

### Are these 5 the only eta quotients that parameterize $x^2+y^2 = 1$?

Given the Dedekind eta function $\eta(\tau)$, define,
$$\alpha(\tau) =\frac{\sqrt2\,\eta(\tau)\,\eta^2(4\tau)}{\eta^3(2\tau)}$$
$$\beta(\tau) =\frac{\eta^2(\tau)\,\eta(4\tau)}{\eta^3(2\tau)}\quad\;$$...

**1**

vote

**0**answers

99 views

### “Modularity” of generalized theta series

The most basic theta series is defined by $\theta(z)=\sum_{n=-\infty}^{\infty}q^{n^2}$, where $q=e^{2\pi iz}$. This is connected to the question of how many representatations does an integer $n$ have ...

**4**

votes

**0**answers

189 views

### What role do Hecke operators and ideal classes perform in “Quantum Money from Modular Forms?”

Cross-posted on QCSE
An interesting application of the no-cloning theorem of quantum mechanics/quantum computing is embodied in so-called quantum money - qubits in theoretically unforgeable states. ...

**1**

vote

**0**answers

82 views

### Igusa curve at infinite level

In the paper "Le halo spectral" (http://perso.ens-lyon.fr/vincent.pilloni/halofinal.pdf) and in the following paper "The adic cuspidal, Hilbert eigenvarieties" (http://perso.ens-lyon.fr/vincent....

**5**

votes

**1**answer

115 views

### Asymptotic's for Fourier coefficients of $GL(3)$ Maass forms

Let $f$ be a $GL(3)$ Hecke-Maass cusp form and $A(m,n)$ denote its Fourier coefficients.
Are there any lower bounds known for $\sum_{p\leq x}|A(1,p)|^2$ or $\sum_{n\leq x}|A(1,n)|^2$ ? (we know the ...