PERSISTENCE LENGTHS OF SEMIFLEXIBLE CHAINS - METHODS AND APPROXIMATIONS

Several models and methods for stiff polymer chains are discussed. The basic idea is to develop approximate solutions to the problem of the persistence length of stiff polymers. It turns out that the persistenc e length can be regarded as a measure for the quality of approximation s. Mean-field methods for field theoretical calculations of the persis tence length show similarities of 1/d expansions in statistical physic s (d being the space dimension) and saddle point approximations become reliable in various limits. Gaussian approximations become - as well known for the Ising model - simple extensions of random walks as trivi al renormalisations of the Wiener-Edwards model for bosonic strings.