Critical dynamics in the pearling instability of membranes

We report quantitative measurements above threshold in the pearling instability of cylindrical membranes. Induced by optical tweezers, the instability propagates outward from the laser trap with well defined wavelength, and velocity. All measured quantities scale with the reduced tension control parameter epsilon = (Sigma - Sigma(c))/Sigma(c). A critical slowing down for initiation of the instability is observed. The values of the velocity, wavelength, and delay time agree with marginal stability and linear analysis. Measurements very close to threshold are strongly masked by thermal fluctuations.