Much progress has been made in the understanding of the general properties of the dielectric function and in the calculation of this quantity for many classes of media. This volume gathers together the considerable information available and presents a detailed overview of the present status of the theory of electromagnetic response functions, whilst simultaneously covering a wide range of problems in its application to condensed matter physics. The following subjects are covered: - the dielectric function of the homogeneous electron gas, of crystalline systems, and of inhomogeneous matter; - electromagnetic fluctuations and molecular forces in condensed matter; - electrodynamics of superlattices.

``Spectroscopy of Crystals Containing Rare Earth Ions'' contains chapters on some key problems selected from a broad range of spectroscopic studies of RE-activated solids including both crystalline and glassy materials. Progress in crystal field theory is surveyed, an area which is basic to our understanding of the energy levels. The treatment of dynamical properties includes studies of coherence phenomena in isolated ions, energy transfer between ions and co-operative phenomena associated with ion-ion and ion-lattice interactions. In addition, the role of electron spins and nuclear spins is studied by light scattering and double resonance techniques. The presence of inhomogeneous broadening of spectral lines is observed and studied in many contexts, leading to new insights into general problems of the disordered state. Considerable attention is devoted to describing new experimental techniques whose development is of prime importance for progress in the spectroscopy of RE-activated solids. Many of these rely on the development and application of tunable lasers. At the moment this is a very active field of spectroscopy with more exciting developments likely to occur in the future.

``Electron-Electron Interactions in Disordered Systems'' deals with the interplay of disorder and the Coulomb interaction. Prominent experts give state-of-the-art reviews of the theoretical and experimental work in this field and make it clear that the interplay of the two effects is essential, especially in low-dimensional systems.

The book provides a review of some of the most important and 'hot' topics in condensed matter physics today. It includes contributions by internationally leading experts such as V M Agranovich, B L Altshuler, E Burstein, V L Ginzburg, K Von Klitzing, P B Littlewood, M Pepper etc, and can serve as a guide-book to modern condensed matter physics.