Author(s): Marco Biroli, Sergio Ciliberto, Manas Kulkarni, Satya N. Majumdar, Artyom Petrosyan, and Grégory Schehr We experimentally study a system of $N=4$ two-dimensional Brownian particles, each confined in a harmonic trap with identical stiffness. The stiffness switches simultaneously between two values at random Poissonian times. This collective switching drives the system into a nonequilibrium stationary s… [Phys. Rev. Lett. 137, 037102] Published Fri Jul 17, 2026