TEP Seminar - Zemin Huang and Gustav John (now at 2:30PM)

Topological defects govern transitions from (quasi-)ordered to disordered phases, exemplified in equilibrium by vortex unbinding at the Berezinskii–Kosterlitz–Thouless (BKT) transition. Far from equilibrium, however, despite the observed proliferation of spacetime vortices, the universal character of the associated transition remains unknown. Here, combining analytical theory with numerical simulations, we uncover a direct link between spacetime-vortex proliferation and directed-percolation criticality. Analytically, we derive a coarse-grained effective theory of the long-wavelength, slow dynamics and show that spacetime vortices generate multiplicative noise in the underlying slow modes, thereby yielding the Reggeon field theory of directed percolation. Numerically, dynamical-scaling analysis yields critical exponents consistent with directed percolation, thereby confirming the analytically predicted universality class.