Cohomology of arithmetic groups and congruences between systems of Hecke eigenvalues.
We give an algorithm to compute the modular degree of an elliptic curve defined over . Our method is based on the computation of the special value at of the symmetric square of the -function attached to the elliptic curve. This method is quite efficient and easy to implement.
Let be a positive integer divisible by 4, a prime, an elliptic cuspidal eigenform (ordinary at ) of weight , level 4 and non-trivial character. In this paper we provide evidence for the Bloch-Kato conjecture for the motives and , where is the motif attached to . More precisely, we prove that under certain conditions the -adic valuation of the algebraic part of the symmetric square -function of evaluated at provides a lower bound for the -adic valuation of the order of the Pontryagin...