Euler’s beautiful formula relating the even values of Riemann’s zeta function to Bernoulli numbers can be seen as the starting point of the investigation of special values of L-functions.

I will describe how the algebraicity of the RM values of rigid meromorphic cocycles might be deduced from the study of the ordinary projections of certain p-adic modular forms of half integral weight, following an approach that is closely modelled on Gross and Zagier’s “analytic proof” of their celebrated theorem on the factorisation of differences…