We give another proof of Imin Chen's result that the jacobian of the modular curve X(p)_{ non-split}, for p a prime number, is isogeneous to the new part of the jacobian of X_0(p^2), using only the representation theory of the group GL_2(Z/pZ). In fact, we prove a generalization of Chen's result for objects with an action by GL_2(Z/pZ) in any pseudo-abelian Q-linear category.
Categories: alg-geom math.AG