Abstract:
 Let X_1(N) be the modular curve associated to the congruence subgroup Gamma_1(N). Its Jacobian J_1(N) contains a rational torsion subgroup coming from the cuspidal divisors of X_1(N). In this talk we will discuss the structure of this rational torsion subgroup. In particular, we will present a structure theorem for the pprimary subgroup of J_1(p^n) in the case when p is a regular prime.
