Quantum theory has an epistemic horizon, i.e. exact values cannot be assigned simultaneously to incompatible physical quantities. As shown by Spekkens' toy theory, positing an epistemic horizon akin to Heisenberg's uncertainty principle in a…

A Planck scale inflationary era—in a quantum gravity theory predicting discreteness of quantum geometry at the fundamental scale—is compatible with observed features in the cosmic microwave background and allows for a hotter big bang which could…

While the action-reaction principle dictates all fundamental physical interactions, the dynamics we effectively observe in complex nonequilibrium systems ubiquitously breaks reciprocity, giving rise to intriguing new physical phenomena.