This proposal belongs to the area of modular forms and L-functions, and it consists of both algebraic and analytic problems related to the structure of the space of modular forms, of integral and half integral weight. The methods I use involve the theory of periods of modular forms, developed in the 1970s by Eichler-Shimura-Manin, and in the 1980s by Kohnen and Zagier. Part of the proposal is conc ...