Long-Range Influence of a Pump on a Critical Fluid

Area of Science:

• Non-equilibrium statistical mechanics
• Critical phenomena
• Soft matter physics

Background:

• Pumps coupled to conserved densities induce long-range modulations due to non-equilibrium dynamics.
• Above the critical point, a pump in a diffusive fluid generates a dipole potential density profile and a dipolar field current.

Purpose of the Study:

• Investigate how pump-induced modulations change at the critical point.
• Characterize the density profile and current behavior at criticality.
• Analyze the effect of a local pump on domain wall structure below criticality.

Main Methods:

• Theoretical analysis of a pump in a diffusive fluid.
• Focus on system behavior at the critical point.
• Application of concepts from critical phenomena, including Ising critical exponents (δ and η).

Main Results:

• The pump-induced current retains its dipolar form at the critical point.
• The density profile at criticality deviates significantly, following a power law dependent on distance (r) and angle (θ).
• A crossover in the density profile occurs at short distances, described by another power law involving Ising exponents.

Conclusions:

• The critical point drastically alters the pump-induced density profile, while the current remains largely unchanged.
• The density deviation at criticality is characterized by universal scaling laws related to Ising critical exponents.
• The study provides insights into non-equilibrium phenomena near critical points and their influence on system structure.