Cycles in Jacobians: infinitesimal results

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Let C be a generic smooth curve of genus g 4. We study normal functions and infinitesimal invariants associated to Ceresa cycles Wₖ-Wₖ⁻, k=2,...,g-2. We show how they can be obtained from the normal function associated to the basic cycle C-C⁻ and, for k=2, we also explicitely determine the zero locus of the infinitesimal invariant. For C hyperelliptic of genus g=3, we define the K-theoretic counterpart of W₂-W₂⁻, generalizing a construction of A. Collino, and show that it is indecomposable.