Long-range influence of a pump on a critical fluid

Abstract

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 $\mathrm{sgn}(\cos (\theta ))|\cos (\theta )/r^{(d-1)}{|}^{1/\delta }$ 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.

5 pages, 1 figure

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Cited by in corpus (1)

• Phase lines in mean-field models with nonuniform external forces