Calculating dynamic structure factors with the real space renormalisation group

Abstract
The authors develop exact methods, based on the real space renormalisation group, for calculating dynamic structure factors of Heisenberg ferromagnets. The method is applied to a pure chain, a Sierpinski gasket and a quasi-one-dimensional model of a dilute chain. The result for the Sierpinski gasket exhibits a rich structure because of the requirement of discrete scale invariance. By the use of the distribution scaling the method is generalised to treat a randomly diluted chain.