Surface Motions and Fluid Dynamics

A certain class of surface motions, including those of a relativistic membrane minimizing the 3-dimensional volume swept out in Minkowski-space, is shown to be equivalent to 3-dimensional steady-state irrotational inviscid isentropic gas-dynamics. The SU($\infty $) Nahm equations turn out to correspond to motions where the time $t$ at which the surface moves through the point $\ssatop\rhup{r}$ is a harmonic function of the three space-coordinates. This solution also implies the linearisation of a non-trivial-looking scalar field theory.