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In simulations of decaying two-dimensional turbulence, Clercx and co-workers discovered the unexpected phenomenon of "spin-up." (This is the spontaneous acquisition of angular momentum by a turbulent two-dimensional fluid in a rigid container.) Here we show that this phenomenon can readily be interpreted in terms of statistical models of two-dimensional turbulence. When the net vorticity is zero in a bounded system, there are two distinct types of statistical equilibrium. The first has the expected property that its angular momentum is zero. However, the second type has a nonzero angular momentum even though its circulation vanishes. The relative probability of the two types of equilibrium depends strongly on the shape of the boundary and weakly on the energy. The angular momentum predicted for the second type of equilibrium is in good agreement with that found in simulations at high Reynolds number.

We develop a theory for the growth of one dimensional (1D) chains stabilized by anisotropic interactions, such as hydrogen bonding. Molecular chains are nucleated, grow, and may then undergo a kinetically driven transition to a two dimensional morphology. Kinetic Monte Carlo simulations show that extended 1D growth occurs between two temperature limits determined by two distinct kinetic instabilities. The limiting temperatures depend on interaction strength and deposition rate and, for a certain parameter range, 1D growth is completely suppressed.

Ripples in the confining field may exert a torque on a rotating plasma. Time reversal symmetry implies that this torque should vanish for an ideal plasma. However, even in an apparently ideal plasma, singularities can give rise to a nonzero torque. This torque is evaluated for a simple configuration. Although the primary force is magnetic, an essential contribution arises from other nonlinear terms in the equations of motion. The net force is confined to the singular layer, in the direction of the ripple wave vector and related to the energy absorbed in the layer.