# Tagged Questions

**3**

votes

**2**answers

173 views

### Interpolation of periods for a Hida family of modular forms

Let $\mathbf{f}$ be a Hida family of ordinary $p$-adic modular forms, and let $V(\mathbf{f})$ be the corresponding $\Lambda$-adic Galois representation (a quotient of the inverse limit
$$ ...

**3**

votes

**1**answer

144 views

### What are the modular transformation properties of q-Pochhammer symbols?

Do q-Pochhammer symbols, defined as
$(a;q) = \prod_{k=0}^{\infty} (1- a q^k)$
have known modular transformation properties? That is, if we write $q = q[z] = e^{2\pi i z}$, is there any reasonably ...

**2**

votes

**1**answer

107 views

### Properties of representations attached to p-adic modular forms

I found an old MOF post about representations attached to p-adic modular forms: Representations attached to p-adic modular forms and I have some follow up questions on the same topic.
If we have a ...

**4**

votes

**0**answers

112 views

### Is there a version of Serre's modularity conjecture for projective representations?

Serre's modularity conjecture asserts that a continuous odd irreducible representation $$\overline{\rho} : G_\mathbb{Q} \rightarrow \mathrm{GL}_2(\mathbb{F}_q)$$ must be modular, in the sense that ...

**6**

votes

**1**answer

209 views

### A conjecture related to the Cohen-Oesterlé dimension formula of spaces of modular forms for half-integer weights

Denote $\operatorname{dim}(M_k(\Gamma_0(N)))$ by $m(k,N)$ and
$\operatorname{dim}(S_k(\Gamma_0(N)))$ by $s(k,N)$.
Let $N$ any positive multiple of $4$ and $j \ge 1$.
$$
a(N) := \frac1j \left(m ...

**15**

votes

**1**answer

490 views

### Ramanujan's pi formulas with a twist

Given the binomial function $\binom{n}{k}$, define the following sequences,
$$\begin{aligned}
u_1(k) &= \tbinom{2k}{k}\tbinom{3k}{k}\tbinom{6k}{3k} = 1, 120, 83160, 81681600,\dots \\
u_2(k) ...

**6**

votes

**2**answers

644 views

### Ramanujan's tau function

Why was Ramanujan interested in the his tau function before the advent of modular forms? The machinery of modular forms used by Mordel to solve the multiplicative property seems out of context until I ...

**4**

votes

**1**answer

170 views

### Theta series for the Leech lattice

The Leech lattice, found by John Leech in 1965, is a fascinating combinatorial object and gives the best possible lattice sphere packing in $\mathbb{R}^{24}$. This result was proved by Cohn and Kumar ...

**20**

votes

**1**answer

771 views

### Is the Modularity Theorem (currently) effective?

The Modularity Theorem says every elliptic curve over $\mathbb{Q}$ can be gotten from the classic modular curve $X_0(N)$ by a rational map. Here $N$ is the conductor, easily calculable from a ...

**3**

votes

**3**answers

381 views

### Modular form on $\Gamma_0(N)$

I recently asked this question on Math.StackExchange with no answer so far. So I thought maybe I can find an answer here.
Let $M(k,\Gamma_0(N))$ be a space of modular forms of weight $k$ on ...

**1**

vote

**0**answers

36 views

### Modular form on $\Gamma_0(N)$ [duplicate]

Let $M(k,\Gamma_0(N))$ be a space of modular forms of weight $k$ on $\Gamma_0(N)$.
Each $f \in M(k,\Gamma_0(N))$ has a Fourier expansion of the form
$$f(\tau)=\sum_{n\in ...

**21**

votes

**0**answers

641 views

### Monstrous Moonshine for Thompson group $Th$?

I. As a background, in Traces of Singular Moduli (p.2), Zagier defines the modular form of weight 3/2,
$$g(\tau) = \frac{\eta^2(\tau)}{\eta(2\tau)}\frac{E_4(4\tau)}{\eta^6(4\tau)}=\vartheta_4(\tau)\, ...

**3**

votes

**1**answer

115 views

### On Universal Abelian surfaces over a Shimura curve.

Let ${\cal O}, {\cal O}'$ be two order in ${\mathrm M}_2({\Bbb R})$ that are sets of all $2 \times 2$ matrices over real number ${\Bbb R}$. Assume that we have the relation ${\cal O}' = a{\cal ...

**2**

votes

**1**answer

135 views

### How to obtain the Period matrix from the Igusa Invariants of a genus two curve?

I am looking for an algorithm to obtain the period matrix tau= (tau1 & tau12\ tau12 & tau2) from the Igusa invariants of a genus two curve. More precisely:
I consider a family of genus two ...

**1**

vote

**0**answers

124 views

### about lemma 5.9 of Mazur's famous Eisenstein ideal paper

In Lemma 5.9 of Chapter II of his famous Eisenstein ideal paper, Mazur proved that
when $1/N$ is invertible in the ring $R$, if $\phi$ is a holomorphic modular form in $\omega^k$ over $\Gamma_0(N)$ ...

**1**

vote

**0**answers

85 views

### another question on the Manin-Drinfeld theorem

A few days ago I asked a question about possible higher dimensional generalizations of the Manin-Drinfeld theorem. Let me come back to the classical statement.
It says that a divisor on the modular ...

**3**

votes

**0**answers

139 views

### Solvable parametric $7$th and $13$th degree equations using $\eta(q)/\eta(q^p)$?

Q: Why is that some polynomial relations between eta quotients have a solvable Galois group, even if the deg is $n>4$?
For example, we have the well-known modular equation,
$$u^6 - v^6 + ...

**4**

votes

**1**answer

219 views

### computing spaces of $p$-adic modular forms

Let $p$ be a prime, and $\alpha$ a positive integer. How do you compute the space of $p$-ordinary $p$-adic modular forms (in the sense of Serre) of weight 2 on $\Gamma_0(p^\alpha)$? I'm really only ...

**34**

votes

**1**answer

1k views

### There's something strange about $\sqrt{d\big(j(\tau)-1728\big)}$

Given the j-function $j(\tau)$, I was looking at,
$$F(\tau) = \sqrt{d\big(j(\tau)-1728\big)}$$
which appears in Ramanujan-type pi formulas. Let $C_d$ be the prime factors of the constant term of the ...

**12**

votes

**2**answers

421 views

### Etymology of cuspidal representations

In the literature on representation theory of $GL_2(\Bbb F_p)$ and $GL_2(\Bbb Q_p)$, the irreducible representations with trivial Jacquet module are often called "cuspidal" or "supercuspidal". Why are ...

**1**

vote

**0**answers

112 views

### A problem involving the converse of Ramanujan's theta operation

Let $A := \mathbb{C}[E_2;E_4,E_6]$ be the algebra of (almost) modular forms for $\mathrm{SL}_2(\mathbb{Z})$. (The weight $2$ Eisenstein series $E_2 := 1 - 24\sum_{n \geq 1} \sigma_1(n)q^n$ satisfies ...

**3**

votes

**2**answers

385 views

### Using Eichler-Selberg trace formula to compute dimension of modular forms?

Is it possible to use Eichler-Selberg trace formula to compute the dimension of modular forms of weight $k$ for $SL(2,\mathbb Z)$? This was computed by classical methods such as Riemann-Roch.

**9**

votes

**1**answer

359 views

### The “Level N modular equation for delta” in characteristics 3, 5, 7 and 13

When $N > 1$, the modular forms $\Delta(z)$ and $\Delta(Nz)$ are algebraically independent over the complexes, and the same then is true of their expansions at infinity. But using the fact that
the ...

**22**

votes

**2**answers

1k views

### Why should I care about topological modular forms?

There seems to be a lot of recent activity concerning topological modular forms (TMF), which I gather is an extraordinary cohomology theory constructed from the classical theory of modular forms on ...

**1**

vote

**0**answers

67 views

### Explicit generators of maximal ideals in completed Hecke algebras

A particular question:
Let M be the subset of Z/3[[x]] consisting of those power series that are reductions of elements of Z[[x]] that arise as expansions of modular forms for Gamma_0 (2). ...

**1**

vote

**0**answers

107 views

### Cube-root of j-invariant [closed]

Cube-root of j-invariant is a modular function of level 3, does it have similar property as j-invariant? How about the its minimal polynomial？ In particular, are it's coefficients much smaller like ...

**5**

votes

**2**answers

309 views

### Representation-theoretic operations on modular forms

Let $A$ and $B$ be Hecke eigenforms of some weight $k$ and level $N$. We know that there are irreducible representations $\rho_a$, $\rho_b$ of the absolute Galois group of $\mathbb{Q}$ whose trace of ...

**18**

votes

**0**answers

545 views

### Eichler-Shimura over Totally Real Fields

By Eichler-Shimura over totally real fields I mean the following conjecture.
Conjecture. Let $K$ be a totally real field. Let $f$ be a Hilbert eigenform with rational eigenvalues, of parallel weight ...

**5**

votes

**2**answers

282 views

### Adelic methods for classical modular forms

Many conjectures about properties of automorphic forms on $\mathrm{GL}(2)$ can be formulated in the basic language of classical modular forms (i.e. Hecke forms that are holomorphic on $\mathbb{H}$ or ...

**5**

votes

**0**answers

148 views

### 4D polytope analogues of the icosahedron/Rogers-Ramanujan continued fraction relationship?

The formula for the j-function which employs polynomial invariants of the icosahedron,
$$j(\tau)=-\frac{(r^{20} - 228r^{15} + 494r^{10} + 228r^5 + 1)^3}{r^5(r^{10} + 11r^5 - 1)^5}$$
where,
...

**3**

votes

**1**answer

265 views

### What does the Jacquet-Langlands correspondence say about quaternion algebras of class number one?

If F is a totally real number field of degree n, and A is a definite quaternion algebra over F, I understand (not really) the Jacquet Langlands correspondence to construct a modular form in n ...

**4**

votes

**2**answers

400 views

### Gross's paper on Heegner points

I try to read Gross's paper on Heegner points and it seems ambiguous for me on some points:
Gross (page 87) said that $Y=Y_{0}(N)$ is the open modular curve over $\mathbb{Q}$ which classifies ordered ...

**5**

votes

**0**answers

318 views

### Benedict Gross's paper on companion forms

In the page 458 of his paper(A tameness criterion for Galois representations associated to modular forms), Gross wrote the following
"A detailed analysis of $U_p(Af)+V_p(<p>f)$ shows that it
...

**3**

votes

**1**answer

148 views

### Real modular form, inverse transform

The real Eisenstein series
$G_s^* = \frac{\Gamma(s)}{\pi^s} \sum'_{m,n}\frac{Im(\tau)}{|m+n \tau|^{2s}}$
admits the following integral representation (their Mellin transform):
$G_s^* = ...

**6**

votes

**1**answer

227 views

### Does the following operation on modular forms yield something modular?

Let $f(z) = \sum_{n=0}^\infty a_nq^n$ be the fourier expansion of a (quasi-)modular form (with $q = e^{2\pi i z}$). Consider the following related functions:
$$f_{m,k}(z) = \sum_{n=0}^\infty a_{mn + ...

**1**

vote

**1**answer

330 views

### stationary phase method in analytic number theory

I hope someone can tell me something about the error term in the formula calculating the oscillatory integral like $\int_a^b g(x)e(f(x))d x$. Specially, the exact formula on page 114 of M. Huxley's ...

**1**

vote

**0**answers

210 views

### in the preface of “A first course in modular forms”

In the preface of "A first course in modular forms", the author considered the quadratic equation $Q: x^2=d, \ \ d \in \mathbb{Z}, d \not=0$, and for each prime $p$ define an integer $a_p(Q)=\#\tilde ...

**20**

votes

**1**answer

792 views

### Monstrous moonshine for $M_{24}$ and K3?

An important piece of Monstrous moonshine is the j-function,
$$j(\tau) = \frac{1}{q}+744+196884q+21493760q^2+\dots\tag{1}$$
In the paper "Umbral Moonshine" (2013), page 5, authors Cheng, Duncan, and ...

**9**

votes

**1**answer

258 views

### The j-function and Pell equations

Given the j-function,
$$j(\tau)=\frac{1}{q}+744+196884q+21493760q^2+\dots$$
it is well-known that for $\tau=\tfrac{1+\sqrt{-d}}{2}$, positive integer $d$, then $j(\tau)$ is an algebraic integer of ...

**21**

votes

**1**answer

1k views

### What is known about the sum x^{n^2}/n?

It follows from a general theorem of Honda that the formal group with the logarithm
$$
x+x^{2^s}/2+x^{3^s}/3+x^{4^s}/4+\cdots
$$
has integer coefficients. I became interested in it because its ...

**5**

votes

**3**answers

437 views

### An attractive introduction to the history of modular forms and its applications

I am a graduate student majoring in number theory. Recently I have to give a report to graduate students studying mathematics. I am interested in this field, but I know little about it. Can you give ...

**1**

vote

**1**answer

159 views

### Does $L(-1+it,f)\ll_f \log^c q(f)t$ hold ture?

Let $f$ be a holomorphic or Maass cusp form for $SL(2,Z)$. Define $L(s,f)=\sum_{n\ge 1}\frac{a_f(n)}{n^s}$, for $\Im s$ sufficiently large.
Then
$$L(-1+it,f)\ll_f \log^c q(f)t$$
holds, for some ...

**7**

votes

**1**answer

183 views

### Existence of CM Newforms in Level p

If $p$ is a prime and $k \geq 2$ is an even integer, what can we say about the existence of CM forms in the space $S_k^\text{new}(\Gamma_0(p))$? If it helps at all, I'm specifically interested in the ...

**4**

votes

**0**answers

195 views

### Deligne-Rapoport stack and reduction mod p of X0(p)

I'm trying to better understand some results contained in Deligne and Rapoport's paper on the moduli spaces of elliptic curves.
For convenience, I'll briefly summarize the parts of the paper that I'm ...

**6**

votes

**0**answers

211 views

### Modular interpretation of Ramanujan theta operator?

I'm a beginner to the theory of modular forms trying to understand a certain construction from the point of view of elliptic curves. Let $f(q) = \sum a_n q^n$ be a formal power series. Define $\theta ...

**8**

votes

**0**answers

179 views

### congruences of level 1 and level p modular forms

I've been carrying out some experiments on the computer and I noticed the following congruence phenomenon: fixing a prime $p$, it seems that any modular form over $SL_2(\mathbb{Z})$ and of weight $k ...

**3**

votes

**1**answer

166 views

### Possible to have Poisson Summation formula with coefficient of modular forms? (for some functions)

Taking a modular form such that we have Fricke involution:
$\sum_{n=1} a_n e^{-\pi nx^2} = \frac{A}{x^k} \sum_{n=1} a_n e^{-\pi \frac{n}{x^2}}$ [1]
I would like to know if there exists results on ...

**1**

vote

**1**answer

117 views

### On properties of coefficients of Selberg Class L-function

The coefficient of Selberg Class L-function satisfy:
$a_n <M_{\epsilon} n^{\epsilon}$ (for any $\epsilon >0$) and the $a_n$ are multiplicative.
So I would like to know if it can be shown that ...

**5**

votes

**1**answer

155 views

### Periods of Twists of Modular Forms

Let $f \in S_2(\Gamma_1(N))$ be an eigenform. By a theorem of Shimura, there are associated "periods" $\Omega_f^\pm$ such that, after normalizing by these periods, the L-function associated to $f$ ...

**1**

vote

**1**answer

107 views

### Bounding the level for eigenforms satisfying a deformation condition

Let $k$ be a finite field of char $p \geq 3$. Given an absolutely irreducible, continuous, odd representation $\overline{\rho}: G_\mathbb{Q} \longrightarrow GL_2(k)$ and a deformation condition $D$ ...