Continuous nonequilibrium transition driven by heat flow.

Area of Science:

• Thermodynamics
• Statistical Mechanics
• Non-equilibrium Physics

Background:

• Understanding non-equilibrium systems is crucial for many physical phenomena.
• Characterizing phase transitions in systems driven out-of-equilibrium remains a challenge.

Purpose of the Study:

• To discover and characterize an out-of-equilibrium phase transition in an ideal gas system.
• To explore the thermodynamic principles governing such transitions.

Main Methods:

• Theoretical analysis of an ideal gas confined between two walls with a movable adiabatic partition.
• Driving the system out-of-equilibrium by direct energy supply into the gas volume.
• Molecular dynamic simulations using a soft-sphere fluid model to validate findings in an interacting system.

Main Results:

• Identified a continuous, out-of-equilibrium transition at a critical heat flux.
• Observed gas separation into distinct hot, low-density and cold, dense regions.
• Confirmed the transition's existence in both ideal and interacting gas systems via simulations.

Conclusions:

• The discovered transition serves as a paradigm for understanding stationary states in non-equilibrium systems.
• Introduced a stationary state Helmholtz-like function for thermodynamic description of these states.
• The findings offer new insights into the behavior of matter under continuous energy flux.