How modes shape Casimir Physics

Modes have steadily influenced the understanding of physical systems through time. At least since the prediction of the Casimir effect, they also play a very important role in Casimir Physics and in the understanding of the different phenomena typical of this research field. At equilibrium modes provide a direct connection between the zero-point energy and the existence of irreducible fluctuations in a quantum system, offering an anatomic view into the physics of the interaction. In nonequilibrium systems, modes can be decisive to understand the behavior of quantum fluctuation-induced phenomena, highlighting key aspects which determine their strength and their functional dependence. In this article we review some recent studies and results that highlight how modes impact Casimir physics and the central role they play in shaping our understanding of this area of research.