Modularity lifting theorems for non-regular symplectic representations

Abstract: We prove an ordinary modularity lifting theorem for certain non-regular 4-dimensional symplectic representations over totally real fields. The argument uses both higher Hida theory and the Calegari-Geraghty version of the Taylor-Wiles method. We also present some applications of these theorems to abelian surfaces. (Joint work with F. Calegari, T. Gee, and V. Pilloni.)