Nonvanishing of quadratic Dirichlet -functions at .
We study the second moment of the central values of quadratic twists of a modular -function. Unconditionally, we obtain a lower bound which matches the conjectured asymptotic formula, while on GRH we prove the asymptotic formula itself.
For an odd prime, we show that the Fekete polynomial has zeros on the unit circle, where . Here is the probability that the function has a zero in , where each is with y . In fact has absolute value at each primitive th root of unity, and we show that if for some then there is a zero of close to this arc.
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