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2 votes

Properties of the ring of all holomorphic modular forms

It may be easier to consider this question for genus zero groups, where we can construct modular forms vanishing at given points in terms of Hauptmoduln. I don't know how to find the divisors in ...
user517604's user avatar
3 votes

Automorphic representation of GL(1)

Using your definition of automorphic representation, the answer to Question 1 is yes, tautologically. If $V_\omega$ is the space of automorphic forms "with character $\omega$" then by ...
Grant B.'s user avatar
  • 506
8 votes

Abscissa of convergence of the $\tau$ Dirichlet series

Consider the sum $$S(x):=\sum_{n\leq x}\frac{\tau(n)}{n^{11/2}}.$$ By Theorem 1.3 in Montgomery-Vaughan: Multiplicative number theory I, the abscissa of convergence equals $$\sigma_c=\frac{11}{2}+\...
GH from MO's user avatar
  • 94.5k
5 votes

Uniqueness of the $J$ invariant

Any meromorphic modular function of weight $0$ for $\mathrm{SL}(2,\Bbb Z)$ is a rational function of $j$, say $P(j)$. Since your function is holomorphic, $P$ is a polynomial. Since your function has a ...
David Loeffler's user avatar
4 votes

How to prove Siegel upper half plane is a hermitian symmetric space

Firstly look at the action of $Sp(2g,\mathbb{R})$ on $\mathbb{H}_g$. As suggested in David E Speyer's answer, the action is given by $M \cdot Z = (AZ + B)(CZ + D)^{-1}$ . Then fix an element in $\...
Peter Wu's user avatar
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