math.AG — Algebraic Geometry
Contributed by Leonardo Finzi
For a curve C and a fixed degree-one divisor e of C, we can embed C into its Jacobian. This embedding induces an algebraic 1-cycle on the Jacobian called the Ceresa cycle, which we denote by Cer(C,e). Although homologically trivial, Ceresa cycles of very general curves with genus ≥3 are non-trivial under algebraic equivalence. It is generally unknown whether a very general curve admits a non-trivial Ceresa cycle modulo rational equivalence. In this paper, we explore the non-triviality under rational equivalence of the Ceresa cycle corresponding to the modular curve X0(N). By extending a method of Lupoian--Rawson involving computing the order of the shadow of the Atkin--Lehner involution wN, we show Cer(X0(kN),e) is non-trivial when N=57,58,77,82,85,88,91,93,111,112,115,123,133,135,141,143,145,147,155,161 for k≥1. Moreover, we detail an algorithm for computing the shadow of the Hecke operator Tℓ for odd primes ℓ not dividing N, which can be used to determine the non-triviality of the Ceresa cycle of X0(N).
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