Universality in many-body driven systems with an umbilic point

We study stationary fluctuations of conserved slow modes in a two-lane model of hardcore particles which are expected to show universal behavior. Specifically, we focus on the properties of fluctuations at a special umbilic point where the characteristic velocities coincide. At large space and time scales, fluctuations are described by a system of stochastic Burgers equations studied recently in Roy et al (2024 J. Stat. Mech. 2024 033209). Our data suggest coupling-dependent scaling functions and, even more surprisingly, coupling-dependent dynamical scaling exponents, distinct from Kardar–Parisi–Zhang scaling exponent typical for surface growth processes.