Transverse fluctuations of polyelectrolytes

The ground state of an N-monomer charged polymer, in the absence of screening, is stretched, with nonextensive energy growing as N lnN. If the allowed bond angles are discrete, only discrete changes in conformation are possible, and the elementary excitations have energy growing as lnN. Using analytical arguments, and Monte Carlo simulations, we show that such a polymer is rigid (flat) at low temperature T, and flexible (rough) at high T. The roughness exponent, for the scaling of transverse fluctuations with N, varies continuously with T, reaching the value for models which permit continuous changes in geometry only at very high T.