Anisotropy can make a moving active fluid membrane rough or crumpled

Abstract: We present a hydrodynamic theory of anisotropic and inversion-asymmetric moving active permeable fluid membranes. These are described by an anisotropic Kardar-Parisi-Zhang equation. Depending upon the anisotropy parameters, the membrane can be large-scale anisotropic and logarithmically rough with translational quasi long range order and orientational long range order, together with the relaxational dynamics being logarithmically faster than ordinary diffusion. For other choices of the anisotropy parameters, the membrane is either effectively isotropic and algebraically rough with translational short, but orientational long range order, or crumpled.