We examine the dynamics of a dimer strongly interacting with noisy quantum reservoirs. This open system, a strongly coupled spin-boson system, is used to model excitation- and charge transfer in quantum chemical and biological reactions (redox, photosynthesis). We analyze the processes using a dynamical quantum resonance theory. Due to the strong coupling, ordinary methods (spectral deformation) cannot be applied, so we develop an extended Mourre theory to construct a resonance expansion of the propagator. In particular, we derive an expression for the reaction rates, proving the celebrated Marcus Formula of quantum chemistry.

In the inflationary paradigm, the very early universe is described using quantum field theory in cosmological space-times. In particular, the origin of the large scale anisotropies in the CMB is traced back to vacuum fluctuations of operators representing cosmological inhomogeneities. However, one then assumes that after a certain stage during inflation, dynamics of these inhomogeneities is well-described by the classical theory. This so-called `quantum to classical transition’ is at first puzzling and has drawn quite a bit of attention. In this talk I will first elucidate this issue, explain why some of the reasoning is incorrect, and arrive at a precise statement of why and how classical behavior emerges. Discussion will not assume any details of inflation, or even cosmology, and will be framed in the language normally used in quantum mechanics.