A rank inequality for the Tate Conjecture over global function fields

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Lyons, Christopher
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Abstract
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Following D. Ramakrishnan, we explain how L. Lafforgue's modularity theorem and an analytic theorem of H. Jacquet and J. Shalika can be applied to prove the following result related to the Tate Conjecture: for a smooth, projective, geometrically-connected variety defined over a global function field, the algebraic rank is less than or equal to the analytic rank. Also discussed is the analogous (open) question for number fields and an easy extension of Lafforgue's theorem to remove the "finite-order character" assumption. All results are likely "known to the experts", but don't appear to be written down.
Comment: Contains correction to statement of main theorem in published version, pointed out by Uwe Jannsen and Dinakar Ramakrishnan. The inequality of the title is unaffected by this
Keywords
Mathematics - Number Theory, Mathematics - Algebraic Geometry, 11G35, 11G40, 11R39, 14G25
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