Nonperturbative vacuum pair creation in strong fields and analogies in graphene

In this thesis, nonperturbative pair creation from the quantum field theoretic ground state in the presence of strong macroscopic gauge fields is studied. Employing different approaches such as the string inspired worldline formalism, the worldline instanton method, semiclassical WKB techniques as well as quantum kinetic theory, we investigate various aspects of this so-called Schwinger effect. More specifically, we study the explicit dependence of the pair production rate on the underlying background structure. Here, we mainly focus on purely time dependent as well as spatiotemporal inhomogeneous and oscillatory electric backgrounds which give rise to substantial enhancement effects. Employing an effective reflection approach, we analyze many properties and characteristic features of the corresponding mechanisms. We also study the impact of microscopic details of the background on nonperturbative and perturbative aspects. Imposing explicit symmetry constraints, we generalize the methods for multidimensional backgrounds which facilitate the nonlocal nature of vacuum pair production. In addition, we investigate analogous effects in condensed matter systems such as bandgapped graphene. Constructing appropriate descriptions in lower dimensional spacetimes via Kaluza-Klein compactifications, we find that creating quasiparticle-hole pairs in this Dirac material resembles pair creation from the quantum vacuum by the dynamical Schwinger mechanism