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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
3 votes
0 answers
235 views

Functional equation link two Dirichlet series

Let $f(z)=\sum_{n\ge 1}a(n)n^{(k-1/2)/2}e(nz)\in S_{k+1/2}(\Gamma_0(4N),\chi)$ be a cuspidal Hecke eigenform. Let $$M(s)=\sum_{p\ge 2, \text{prime}}\frac{|a(p)|^2}{p^s}$$ and $$R_f(s)=\sum_{n\ge 1}\...
Med's user avatar
  • 400
3 votes
1 answer
344 views

Estimate the ratio $\dfrac{\left(\sum_{n\le X}a(n)\right)^2}{\underset{n\le X}{\sum} a(n)^2}$

Let $f=\sum_{n\ge 1} a(n)q^n\in M_{k+\frac{1}{2}}(\Gamma_0(4N),\chi)$ be a modular form of half-integral wieght. Can someone prove or disprove that: $$X\ll \dfrac{\left(\sum_{n\le X}a(n)\right)^2}{\...
user95750's user avatar
0 votes
1 answer
218 views

Clarification of the proof of the main theorem of the paper of Hulse et al

I am trying to understand some open steps in the following article The Sign of Fourier coefficients of Half-integral Weight Cusp Form by Hulse, Kiral, Kuan, and Lim, I find the following : Let $f\...
Med's user avatar
  • 400
8 votes
1 answer
739 views

Average of Fourier coefficients of a cusp form of half integral weight

Suppose $f$ is a cusp form of half integral weight $k$ w.r.t. the group $\Gamma_0(4)$ ($k$ is not very low, can assume $k \ge 11/2$), and $a_n$ is its Fourier coefficient. The Linnik bound says that ...
Fan Zheng's user avatar
  • 5,169