The K.P. Hypothesis for decomposable Abelian Varieties.
For an Abelian Variety , the Künneth decomposition of the rational equivalence class of the diagonal gives rise to explicit formulas for the projectors associated to Beauville's decomposition (1) of the Chow ring , in terms of push-forward and pull-back of -multiplication. We obtain a few simplifications of such formulas, see theorem (4) below, and some related results, see proposition (9) below.
By the fundamental work of Griffiths one knows that, under suitable assumption, homological and algebraic equivalence do not coincide for a general hypersurface section of a smooth projective variety Y. In the present paper we prove the same result in case Y has isolated singularities.
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