Driven dissipative dynamics in an open many-body quantum system

In a large variety of systems in nature, a small change of an external parameter around a critical value could affect the microscopic dynamics in such a deep way that the entire system changes sharply its macroscopic state and properties, experiencing what is known as a phase transition. Non equilibrium phase transitions are a particular class of phase transitions which occur in systems far from the thermal equilibrium. An example is that of absorbing state phase transitions, in which the behaviour of the system is determined by the competition of two processes, where one increases the order parameter of the transition, while the other lowers it. The system thus ends in one of two different states, either an oscillating state, or an absorbing state in which the order parameter equals zero and from which the system cannot escape. An example is represented by the infectious spreading of a disease, in which the two processes are the infection and the spontaneous healing, while the two final states are a partially infected or a completely healed population.