Fractal structure of the effective action in (quasi)planar models with long-range interactions

We derive the effective potential for composite fields in a class of (quasi)planar models with long-range interactions. This class of models can be relevant for high temperature superconductors and graphite. The fractal structure of the effective potential is revealed and its physical interpretation is presented. It is argued that the multi-branched fractal structure of the potential reflects the presence of an infinite tower of excitonic bound states that occur as a result of the long-range interactions. (C) 2003 Elsevier B.V. All rights reserved.