Abstract:
In despair, as Deligne put it, of proving the Hodge and Tate conjectures, one can try to find substitutes. For abelian varieties in characteristic zero, Deligne in his 1978–1979 IHES seminar constructed a theory of Hodge classes having many of the properties that the algebraic classes would have if the Hodge conjecture were known. In this article I investigate whether there exists a theory of “rational Tate classes” on varieties over finite fields having the properties that the algebraic classes would have if the Hodge and Tate conjectures were known. In particular, I prove that there exists at most one “good” such theory.
Key words and phrases:abelian varieties, finite fields, Tate conjecture.