Long-Range Influence of a Pump on a Critical Fluid

A pump coupled to a conserved density generates long-range modulations, resulting from the non-equilibrium nature of the dynamics. We study how these modulations are modified at the critical point where the system exhibits intrinsic long-range correlations. To do so, we consider a pump in a diffusive fluid, which is known to generate a density profile in the form of an electric dipole potential and a current in the form of a dipolar field above the critical point. We demonstrate that while the current retains its form at the critical point, the density profile changes drastically. At criticality, in d < 4 dimensions, the deviation of the density from the average is given by sgn[cos(theta)]vertical bar cos(theta)/r((d-1))vertical bar(1/delta) at large distance r from the pump and angle theta with respect to the pump's orientation. At short distances, there is a crossover to a cos(theta)/r(d-3+eta) profile. Here delta and eta are Ising critical exponents. The effect of the local pump on the domain wall structure below the critical point is also considered.

Automated summary

This study investigates the effects of a pump on the density profile and current in a diffusive fluid at the critical point. The results show that the density profile undergoes significant changes at criticality, while the current remains unchanged. The deviation of the density from the average at large distances and specific angles can be described by a specific formula. The study also considers the impact of the local pump on the domain wall structure below the critical point.