The aim of Letters in Mathematical Physics is to present to the specialized reader (from graduate-level student upwards) important new developments in the area of mathematical physics. The journal is a vehicle for the rapid communication of short contributions and contains letters and, occasionally, short review articles and research projects in the fields of: modern group theory and applications to physics; quantum-field theory; mathematical models for physical systems; classical, quantum and statistical mechanics; relativity and gravitation, etc. It offers, in addition, important contributions to modern mathematics in such fields as functional analysis, differential geometry, algebra, topology, etc., which have a potential physical application, and important developments in theoretical physics which have potential mathematical impact.