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Counterexamples related to the Sato-Tate conjecture

File(s)
Miller_cornellgrad_0058F_10258.pdf (452.88 KB)
Permanent Link(s)
https://doi.org/10.7298/X4PN93Q3
https://hdl.handle.net/1813/51667
Collections
Cornell Theses and Dissertations
Author
Miller, Daniel Keegan
Abstract

Let $E_{/\mathbf{Q}}$ be an elliptic curve. The Sato--Tate conjecture, now a theorem, tells us that the angles $\theta_p =\cos^{-1}\left(\frac{a_p}{2\sqrt p}\right)$ are equidistributed in $[0,\pi]$ with respect to the measure $\frac{2}{\pi}\sin^2\theta, d\theta$ if $E$ is non-CM (resp.~$\frac{1}{2\pi} d \theta + \frac 1 2 \delta_{\pi/2}$ if $E$ is CM). In the non-CM case, Akiyama and Tanigawa conjecture that the discrepancy [ D_N = \sup_{x\in [0,\pi]} \left| \frac{1}{\pi(N)} \sum_{p\leqN} 1_{[0,x]}(\theta_p) - \int_0^x \frac{2}{\pi}\sin^2\theta, d\theta\right| ] asymptotically decays like $N^{-\frac 1 2+\epsilon}$, as is suggested by computational evidence and certain reasonable heuristics on the Kolmogorov--Smirnov statistic. This conjecture implies the Riemann hypothesis for all $L$-functions associated with $E$. It is natural to assume that the converse (generalized Riemann hypothesis implies discrepancy estimate'') holds, as is suggested by analogy with Artin $L$-functions. We construct, for compact real tori, fake Satake parameters'' yielding $L$-functions which satisfy the generalized Riemann hypothesis, but for which the discrepancy decays like $N^{-\epsilon}$ for any fixed $\epsilon>0$. This provides evidence that for CM abelian varieties, the converse to ``Akiyama--Tanigawa conjecture implies generalized Riemann hypothesis'' does not follow in a straightforward way from the standard analytic methods. We also show that there are Galois representations $\rho\colon Gal(\overline{\mathbf{Q}} /\mathbf{Q}) \to GL_2(\mathbf{Z}l)$, ramified at an arbitrarily thin (but still infinite) set of primes, whose Satake parameters can be made to converge at any specified rate to any fixed measure $\mu$ on $[0,\pi]$ for which $\cos\ast\mu$ is absolutely continuous with bounded derivative.

Date Issued
2017-05-30
Keywords
Dirichlet series
•
discrepancy
•
Galois representations
•
Sato-Tate conjecture
•
Mathematics
Committee Chair
Ramakrishna, Ravi K
Committee Member
Speh, Birgit E M
Zywina, David J
Degree Discipline
Mathematics
Degree Name
Ph. D., Mathematics
Degree Level
Doctor of Philosophy
Type
dissertation or thesis

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