High-speed video data for settling of dense liquid droplets through liquid media with different viscosities.

A dataset of high-speed video footage of mercury droplets settling through liquid media of different viscosities is presented. Video footage was taken at 4000 frames per second for mercury droplets at room temperature settling through either deionised water or silicone oil. The data set is useful for validation of computational models of a wide range of systems which include phase separation studies, settling behaviour as well as interfacial phenomena in liquid-liquid systems.

Resonantly driven wobbling kinks.

The amplitude of oscillations of the freely wobbling kink in the varphi(4) theory decays due to the emission of second-harmonic radiation. We study the compensation of these radiation losses (as well as additional dissipative losses) by the resonant driving of the kink. We consider both direct and parametric driving at a range of resonance frequencies.

Wobbling kinks in varphi(4) theory.

We present a uniform asymptotic expansion of the wobbling kink to any order in the amplitude of the wobbling mode. The long-range behavior of the radiation is described by matching the asymptotic expansions in the far field and near the core of the kink. The complex amplitude of the wobbling mode is shown to obey a simple ordinary differential equation with nonlinear damping.

Moving solitons in the discrete nonlinear Schrödinger equation.

Using the method of asymptotics beyond all orders, we evaluate the amplitude of radiation from a moving small-amplitude soliton in the discrete nonlinear Schrödinger equation. When the nonlinearity is of the cubic type, this amplitude is shown to be nonzero for all velocities and therefore small-amplitude solitons moving without emitting radiation do not exist. In the case of a saturable nonlinearity, on the other hand, the radiation is found to be completely suppressed when the soliton moves at one of certain isolated "sliding velocities.

Translationally invariant discrete kinks from one-dimensional maps.

For most discretizations of the phi4 theory, the stationary kink can only be centered either on a lattice site or midway between two adjacent sites. We search for exceptional discretizations that allow stationary kinks to be centered anywhere between the sites. We show that this translational invariance of the kink implies the existence of an underlying one-dimensional map phi(n+1) =F (phi(n)) .