  Absorbing phase transitions (APTs) are widespread in non-equilibrium systems,
spanning condensed matter, epidemics, earthquakes, ecology, and chemical
reactions. APTs feature an absorbing state in which the system becomes
entrapped, along with a transition, either continuous or discontinuous, to an
active state. Understanding which physical mechanisms determine the order of
these transitions represents a challenging open problem in non-equilibrium
statistical mechanics. Here, by numerical simulations and mean-field analysis,
we show that a quasi-2d vibrofluidized granular system exhibits a novel form of
APT. The absorbing phase is observed in the horizontal dynamics below a
critical packing fraction, and can be continuous or discontinuous based on the
emergent degree of synchronization in the vertical motion. Our results provide
a direct representation of a feasible experimental scenario, showcasing a
surprising interplay between dynamic phase transition and synchronization.
