Hi all, Next week, Simon Fuchs will talk about “Classical physics as the coarse-grained limit of quantum mechanics”. See below for the abstract. The talk will take place on Monday at 15:00 in HIT K52. Best, Ladina %%%%%%%%%%%% Title: Classical physics as the coarse-grained limit of quantum mechanics Abstract: In this talk, I will discuss how classical behaviour emerges from quantum mechanics when observations are restricted to coarse-grained measurements. Building on earlier work at IQOQI, we argue that, when measurements cannot resolve the intrinsic spread of the wavefunction, coherence averages out and statistics appear classical. Such coarse measurements can be modeled by projections onto coherent states, an overcomplete basis that defines an effective phase space. Dynamically, the Ehrenfest theorem ensures approximate Newtonian trajectories, while decoherence suppresses corrections. Beyond kinematics and dynamics, this framework also hints at an emergent classical geometry, where phase-space distances correspond to the quantum distinguishability of coherent states. Finally, I will discuss extensions of this approach to relativistic systems. While it yields consistent, frame-dependent classicality conditions for massive particles, it encounters fundamental obstacles for massless ones due to the non-compact little group of lightlike momenta. This difficulty may help explain why classical massive objects are typically described as particles, whereas massless ones are treated as fields.