Emergent horizons in the laboratory

Abstract

The concept of a horizon known from general relativity describes the loss of causal connection and can be applied to non-gravitational scenarios such as out-of-equilibrium condensed-matter systems in the laboratory. This analogy facilitates the identification and theoretical study (e.g., regarding the trans-Planckian problem) and possibly the experimental verification of ‘exotic’ effects known from gravity and cosmology, such as Hawking radiation. Furthermore, it yields a unified description and better understanding of non-equilibrium phenomena in condensed-matter systems and their universal features. By means of several examples including general fluid flows, expanding Bose–Einstein condensates and dynamical quantum phase transitions, the concepts of event, particle and apparent horizons will be discussed together with the resulting quantum effects.