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111 views

Whether or not the root number of GL$_3\times$GL$_2$ $L$-function $L(s, F \otimes g)$ contains the coefficients $\lambda_g(n)$ of $g$?

$\DeclareMathOperator\GL{GL}\DeclareMathOperator\SL{SL}$Let $p$ and $q$ be two distinct primes. Let $$\Gamma_0(p)= \left\{ g\in \GL_3(\mathbb{Z}):g \equiv \left(\begin{matrix} \ast &\ast&\...
hofnumber's user avatar
3 votes
0 answers
190 views

Voronoi formula on $\mathrm{GL}_4$ in the level aspect with ramification

$\DeclareMathOperator\GL{GL}$Let $f$ be an automorphic form on $\GL_3$ for $\Gamma_0(p)$ with $p$ being a prime (see Bump or Goldfeld's books for definitions). Recall that, in this paper-"The ...
hofnumber's user avatar
0 votes
2 answers
223 views

What is the definition of Tr in the context of Hilbert modular forms?

I am currently reading Garrett's book "Holomorphic Hilbert Modular Forms". But I meet trouble at the starting line. Let $F = \mathbb{Q}(\sqrt D)$ be a real quadratic field, $u= a + b\sqrt{D}\...
Misaka 16559's user avatar
8 votes
1 answer
356 views

Average bounds on Rankin-Selberg coefficients for modular forms

Let $f$ be a cuspidal Hecke newform of weight $k$ and level $N$, and denote by $a_f(n)$ its $n$-th Fourier coefficient. The newform $f$ is normalized so that $a_f(1) = 1$. As a consequence of Rankin-...
Desiderius Severus's user avatar
3 votes
1 answer
228 views

On the local factor of Rankin-Selberg L-functions

I have a puzzle on the local factors of Rankin-Selberg $L$-functions. Consider two newforms on $\text{GL}_2$. Let $f$ be a newform of square-free level $N$, and $g$ a newform of trivial level. As ...
FeiHou's user avatar
  • 353
2 votes
1 answer
147 views

Finiteness and bounds for elliptic curves realizing a given galois representation

Let $\rho: \text{Gal}(\overline{\mathbb{Q}}/\mathbb{Q}) \to \text{GL}_2(\mathbb{Z}_p)$ be a continuous, irreducible Galois representation. Consider the set $\mathcal{L}_\rho$ of all elliptic curves $...
Thomas Frenkel's user avatar
5 votes
0 answers
126 views

Using Lang–Trotter to get bounds on averages of Fourier coefficients

Let $E$ be an elliptic curve over $\mathbf{Q}$ and let $(a_n)$ be the sequence of Fourier coefficients for the weight two newform attached to $E$. The coefficients $a_p$ are the Frobenius traces given ...
Joseph Harrison's user avatar
3 votes
0 answers
122 views

Is there any notion of Poincaré series for Hermitian modular forms?

I have been studying modular forms and their generalisations for a year or so. It is a very interesting fact that the space of cusp forms $S_k$ is generated by the Poincaré series of exponential type (...
Ancient Antagonist's user avatar
2 votes
1 answer
229 views

Generating function over primes in an arithmetic progression

Given a newform $\sum_{n=1}^{\infty}a(n)q^n$. Is the generating function $$ \sum_{p\equiv a\pmod{m}}a(p)q^p $$ over the primes $p\equiv a\pmod{m}$ still a modular form? Any help is highly appreciated! ...
ModularForms's user avatar
4 votes
1 answer
229 views

Abscissa of convergence of the $\tau$ Dirichlet series

Define the $\tau$ Dirichlet series $L$ by $$L(s)=\sum_{n=1}^\infty \frac{\tau (n)}{n^s}$$ where $\tau$ is defined by $$q\prod_{n=1}^\infty (1-q^n)^{24}=\sum_{n=1}^\infty \tau (n)q^n$$ where $|q|\lt 1$....
Nomas2's user avatar
  • 317
2 votes
1 answer
147 views

On the square mean of Fourier coefficients of cusp forms

I have a question which may look naive for many experts here: For any primitive holomorphic form $f$ of level $M$ ($M\in \mathbb{N}$), whether or not one has the lower bound that: $$\sum_{X<n\le 2X}...
hofnumber's user avatar
  • 563
4 votes
1 answer
192 views

Identity related to Ramanujan's congruences

A very simple question: how do you prove the following identity: $$\sum_{k=0}^\infty p_{5k+4}x^k=5\frac{\phi(x^5)^5}{\phi(x)^6},$$ where $$\phi(x)=\prod_{n=1}^\infty 1-x^n,$$ and $p_n$ is the ...
Alexander's user avatar
1 vote
0 answers
167 views

On two formulas involving the $k$-fold divisor function $d_k$ and the function $r_k$

I have a puzzle which needs some help form the experts here. Let $d(n)$ be the divisor function, and $d_k(n)$ the $k$-fold divisor function. I) It is known that, for any positive integer $h$, $$d(n+h)...
hofnumber's user avatar
  • 563
2 votes
0 answers
286 views

Is Sturm's theorem able to do these?

$\newcommand{\Ord}{\operatorname{Ord}}$Let $p$ be a positive integer and $F(q)=\sum A(m)q^m$ be a formal power series with integer coefficients. Then $\Ord_p(F(q))$ is defined by $$\Ord_p(F(q)):=\min\{...
T. Amdeberhan's user avatar
4 votes
1 answer
299 views

The Wilton-type bounds involving half-integral weight cusp forms

There is a basic question which puzzles me for a while, and maybe look naive for some experts here. The question is the following: Let $f(z)=\sum_{n\ge 1} a_f(n) n^{k/2-1/4}e(nz)\in S_{k+1/2}(4N)$ be ...
hofnumber's user avatar
  • 563
3 votes
1 answer
237 views

Experiments with Voronoï summation

In order to test my understanding of the Voronoï summation formula, I tried to apply it to a simple estimation of partial sums of Fourier coefficients of cusp forms. The result I obtained cannot ...
user50139's user avatar
  • 545
1 vote
0 answers
87 views

what is the relationship betwen $L(s,sym^mf\times sym^mg)$ symmetric L function of $f$ and $g$ and $\lambda_{f}(n^m)$, $\lambda_{g}(n^m)$?

what is the relationship betwen $L(s,sym^mf\times sym^mg)$ symmetric L function of $f$ and $g$ and $\lambda_{f}(n^m)$, $\lambda_{g}(n^m)$ ?
Li Xnu's user avatar
  • 11
2 votes
1 answer
219 views

Voronoï summation for cusp forms with characters

In an attempt to solve an unrelated problem, I was led to the task of estimating/bounding from above sums of the form $$\sum_{m=1}^\infty\lambda(m)e\left(-\frac{am}{q}\right)h(m)$$ where $\sum_{m=1}^\...
user50139's user avatar
  • 545
2 votes
0 answers
98 views

Extrema of real analytic Eisenstein series and more general modular functions

The real analytic Eisenstein series defined by the Poincare sum $$E(s,z)=\sum_{(m,n)\neq (0,0)} {y^s\over |mz+n|^{2s}}$$ for $z\in{\mathbb H}$ and ${\rm Re}(s)>1$ is a manifestly $SL(2,{\mathbb Z})$...
Yifan's user avatar
  • 21
2 votes
0 answers
137 views

Entropy of a sequence

I am reading the paper Sign Changes in Hecke Eigenvalues by Matomaki and Radziwill, and in one place they mention the following, It would be interesting to rule out the possibility of $\lambda_f(n)$ ...
Krishnarjun's user avatar
7 votes
1 answer
264 views

Upper bound of the analytic rank of the modular Jacobian varieties $J_1(N)$

Does there exist an upper bound of the analytic rank of the modular Jacobian varieties $J_1(N)$? (Or more generally of $J_\Gamma$ for a congruence subgroup $\Gamma_0 \subseteq \Gamma \subseteq \...
k.j.'s user avatar
  • 1,364
4 votes
0 answers
509 views

Ramanujan's conjecture on modular forms and Riemann hypothesis

I just watched Kannan Soundararajan's talk on the distributions of valus of zeta and $L$-functions at virtual ICM 2022. In his talk, he introduced a theorem on Ramanujan's ternary form $\phi_{1}: x^{2}...
Seewoo Lee's user avatar
  • 2,215
1 vote
0 answers
103 views

Global irreducible admissible representations analogue

Let ${A}_{\mathbb{Q}}$ denote the adele over the rational numbers. Then it is known that cuspidal modular forms of level $N$ correspond to some unitary automorphic representation of $\operatorname{GL}...
Akash Yadav's user avatar
7 votes
1 answer
435 views

Fricke involution and Atkin operator

Let $f\in S_k(\Gamma_0(N))$ be a cusp form for $N>1$. Consider the following operators acting on $f$ via the natural action of $GL_2^{+}(\mathbb{R})$ : $$ W_N=\begin{pmatrix} 0 & -1\\ N & 0 ...
Akash Yadav's user avatar
4 votes
0 answers
204 views

A question on the twisted symmetric square L-functions

Sorry to disturb. I have a puzzle which might be naive for many experts here. Let $f$ be a Hecke newform of prime level $N$ on $\mathrm{GL}_2$, and $ \chi$ a primitive character of square-free ...
FeiHou's user avatar
  • 353
1 vote
0 answers
109 views

Whether or not the Maass form for $\Gamma _0(N)$ on $GL(3)$ covers the classical symmetric lift of a newform on $GL(2)$?

I have a blur which needs some help from the experts here, and may look naive for some experts. Recently I read Zhou's paper "The Voronoi formula on $GL{(3)}$ with ramification" (https://...
hofnumber's user avatar
  • 563
0 votes
1 answer
163 views

Lower bound related to derivative of $j$-invariant

Recall the $j$-invariant function, namely, $$ j(\tau)=\frac{1}{q}+\sum_{k\geq 0}c_kq^k, $$ where $q=e^{2\pi i \tau}$ and the coefficients $(c_k)_k$ are in the OEIS sequence A000521. By using some ...
Jean's user avatar
  • 515
3 votes
3 answers
483 views

Growth of the coefficients of the inversion of the $j$-invariant function

We have the $j$-invariant defined as I have that $$ j(\tau)=\frac{1}{q}+\sum_{k\geq 0}c_kq^k, $$ where $q=e^{-2\pi t}$ ($\tau=it$) and $c_k\sim e^{4\pi\sqrt{k}}/(k^{3/4}\sqrt{2})$. The inversion ...
Jean's user avatar
  • 515
6 votes
0 answers
456 views

Conditions under which an $\eta$-quotient becomes a **weak** modular form (reference request for theorems similar to Ligozat's theorem)

For any $z \in \mathcal{H}$, let $q = e^{2\pi iz}$; and the eta function is defined as ${\displaystyle \eta (q) =q^{\frac {1}{24}}\prod _{n=1}^{\infty }\left(1-q^{n}\right).}$ By an $\eta$-quotient ...
Davood Khajehpour's user avatar
2 votes
1 answer
159 views

On some claims on cyclic modules over Hecke algebra used in Serre's "Quelques applications du théorème de densité de Chebotarev"

I have been reading section 7 of Serre's "Quelques applications du théorème de densité de Chebotarev" (http://www.numdam.org/item/PMIHES_1981__54__123_0/), and in particular have been trying ...
asrxiiviii's user avatar
2 votes
0 answers
245 views

Ambiguity about the exact definition of coefficients of modular forms

You can see the parts after my questions in the boxes. I received the answer to my first question in the comments. I am confused about the definition of $a_n$ and $b_n$ in Part II below. I know the ...
Tireless and hardworking's user avatar
2 votes
0 answers
270 views

Generalized Siegel Weil formula

I am studying the following Poincare-like series, \begin{equation} F_k(\tau,\bar{\tau})=\sum_{\gamma\in\Gamma_{\infty}\backslash\Gamma}\sqrt{\text{Im}\gamma\tau}(q_{\gamma}\bar{q}_{\gamma})^k, \end{...
Sounak Sinha's user avatar
4 votes
0 answers
135 views

Values at 1 of symmetric power L-functions of Maass cusp forms

I have a blur that whether one has $L(1,\text{sym}^2f)\ll \log^A q$ for some $A>0$? Here $f$ is assumed to be a Maass cusp form of square-free level $q$. If any experts here know something about ...
hofnumber's user avatar
  • 563
5 votes
1 answer
358 views

Coefficients of modular forms and the Sato-Tate distribution

Let $a(n)$ be the $n$th Fourier coefficient of a normalized Hecke eigenform $f(z)=\sum_{n=1}^{\infty}a(n)q^n$ of weight $k$ with respect to the full modular group, where $q=e^{i2\pi z}$. A new paper [...
KQR32DP's user avatar
  • 51
4 votes
0 answers
204 views

$\DeclareMathOperator\sym{sym}$Does $L(s, \sym^2 f \times \sym^2 g)$ have a pole at $s=1$?

$\DeclareMathOperator\SL{SL}\DeclareMathOperator\GL{GL}\DeclareMathOperator\sym{sym}$I encountered a question on the poles of $\GL_3\times \GL_3$ $L$-function, which needs the knowledge of the experts ...
hofnumber's user avatar
  • 563
1 vote
1 answer
323 views

How to relate Rankin triple L-function to its Dirichlet series

I have a very tricky question which may look naive to many experts here. Let $f$ be a newform of level prime $P$, and $g,h$ two newforms of level 1, respectively. These three forms $f,g,h$ are all of ...
hofnumber's user avatar
  • 563
6 votes
2 answers
392 views

A lower-bound for the square-mean of Fourier coefficients of cusp forms at primes argument

There is a basis question which puzzles me for a while. The question is the following: Let $X\ge 2,$ and $\lambda(n)$ be the $n$-th Fourier coefficient of a $GL(2)$ newform of prime level $N>1$, ...
hofnumber's user avatar
  • 563
9 votes
0 answers
208 views

Unexpected patterns on the graph of an L-function on the critical line

Let $L(s)$ be the $L$-function associated to the (only) classical modular form of weight $26$ and level $1$. The completed L-function $\Lambda(s)=2(2\pi)^{-s}\Gamma(s) L(s)$ is symmetric with respect ...
LeechLattice's user avatar
  • 9,501
10 votes
2 answers
1k views

Modular forms with finitely many or very few non-zero Fourier coefficients

I have an elementary question on modular forms, but which I don't know how to solve. a) Is there a congruence subgroup $\Gamma \leq \mathrm{SL}_2(\Bbb Z)$, an integer $k \in \Bbb Z$ and a non-...
Alphonse's user avatar
  • 255
2 votes
0 answers
86 views

Ordinary primes for a weak form corresponding to a CM newform

Setup: Let $f$ be a harmonic Maass form of weight $2-k$ ($k \in \mathbb{N}$), level $N$, and character $\chi$. Letting $q := e^{2\pi i z}$ and considering the Fourier expansion of any harmonic Maass ...
Freddie's user avatar
  • 26
3 votes
0 answers
186 views

Maximum value of newform from Galois representation

One can attach $\ell$-adic Galois representations to holomorphic cuspidal newforms of weight $2$ on the upper half-plane. If a newform is $L^2$-normalized, can one extract its maximum value from the ...
sup's user avatar
  • 39
1 vote
0 answers
132 views

Stabilizers of points in the upper half-plane

Suppose that $\Gamma$ is a group acting discontinuously on $\mathcal{H} = \{ z \in \mathbb{C} : \operatorname{Im}(z) > 1\}$. In order to keep things simple, suppose that $\Gamma \subseteq \...
Oiler's user avatar
  • 163
1 vote
0 answers
129 views

Siegel's formula for generalized theta series with characteristics?

Siegel's formula(Siegel-Weil) directly relates the weighted sum of theta functions to Eisenstein series. (Or equivalently, the weighted sum of the cusp form is zero). I wonder if there is a ...
Y.J.'s user avatar
  • 11
2 votes
1 answer
163 views

Theta series analogues for higher degree forms

It is simple to see that the following series converges absolutely and uniformly on $\mathcal{H}$ for all k positive: $F_{2k}(z) = \sum_{n \in \mathbb{Z}} q^{n^{2k}}$ And this series being a ...
Sagars's user avatar
  • 73
4 votes
0 answers
288 views

Lower bound on symmetric square L-function

In a paper of Soundararajan, equation (16c) states that for any Hecke eigenform $f$ of weight $k$, the symmetric square L-function at $1$ satisfies the bound $$(\log k)^{-2}\ll L(1, \mathrm{sym}^2f)\...
Mayank Pandey's user avatar
8 votes
2 answers
744 views

A question related to Hilbert modular form

This is a question related to Hilbert modular forms. Let $\mathbb{K}=\mathbb{Q}(\sqrt D)$ be an imaginary quadratic field with discriminant $D<0$ and $\zeta (\text{mod } m)$ a Hecke character such ...
user15243's user avatar
  • 424
4 votes
1 answer
282 views

Mean square estimate for the Kloosterman sums

For $m,n\in \mathbb{N}$, denote the Kloosterman sum $$S(m,n;c)=\sum_{a\bmod c}e\left( \frac{ma+n \overline{a}}{c}\right),$$where $\overline{a}$ denotes the multiplicative inverse of $a\bmod c$. Does ...
FeiHou's user avatar
  • 353
5 votes
1 answer
544 views

(Explicit) Basis for Kohnen's plus-space of modular forms of half integral weight

Sorry if this is trivial, but I could not find any reference. Let $k,a,b$ be integers. The space of modular forms of integer weight $M_k(\text{SL}_2(\mathbb{Z}))$ admits a basis of the form $\{ E_4^...
1.414212's user avatar
  • 367
1 vote
0 answers
65 views

Meaning of extended principal part of weakly holomorhpic modular forms

In p.312 of 'Rhoades, Robert C., Linear relations among Poincaré series via harmonic weak Maass forms. Ramanujan J. 29 (2012), no. 1-3, 311–320', the author defines the extended principal part at ...
LWW's user avatar
  • 663
3 votes
1 answer
341 views

Siegel's bad character

Let $K$ be an imaginary quadratic field with discriminant $d_K$. Suppose that $d_K=gt$, where either $g,t$ are discriminants or have the value $g=1,t=d$. Let $f$ be an additional discriminant of a ...
Shimrod's user avatar
  • 2,375