A polymer chain in an annealed random medium: the puzzle of fisher renormalization

Abstract

We propose that a transition to a collapse phase by annealed disorder leads to the nonapplicability of Fisher renormalization which sometimes gives meaningless values for the polymer size exponent. This is shown, in the field-theoretic approach, by identifying an important term in the Hamiltonian of a polymer in a binary mixture that shows a runaway behaviour under a renormalization group transformation.