Olivier Taïbi: Cohomology of local systems on A_g and Spin Galois representations

I will explain the description of the cohomology of certain l-adic local systems on the moduli stack \(\mathcal{A}_g\) of principally polarised abelian varieties of dimension g (i.e. level one Siegel modular varieties) in terms of Galois representations taking values in GSpin groups.