Granular polymer solution

We have measured the spectrum of fluctuations in the size of a granular polymer in a granular solvent. The system consists of a linear chain of plastic spheres immersed in a planar fluid of self-propelled balls. The time average of the end-to-end length r of the chain scales with the number of links N according to approximately N2nu, with nu=0.75+/-0.01. This provides an experimental test of the theoretical value nu=3 / 4 of the critical exponent for a self-avoiding random walk in two dimensions. The measured probability distribution P(r) is compared with the universal function of the scaling theory.