STATIC AND DYNAMIC ASPECTS OF DISORDER LINES

Using one-dimensional models, we characterize the existence of a disorder line (point) in a renormalization group procedure. This procedure is defined in terms of the eigenvalues of the transfer matrix. There are various possibilities for the crossing of subdominant eigenvalues; this study therefore encompasses usual disorder lines (where the spin-spin correlation function changes), as well as other types of disorder lines (where, for instance, the energy-energy correlation function changes). In the usual case, the disorder line shows up as a separatrix between two regions of the flow diagram attracted to different paramagnetic sinks. For this case, we also consider, in the framework of the random phase approximation, the dynamical signature of a disorder line: we show that it can be experimentally detected, especially for disorder lines (points) of the second kind.