Recent developments in Reggeon field theory

In the last few years Reggeon Field Theory (RFT) has been developed into a very powerful tool for analyzing the complex angular momentum structure of high energy scattering amplitudes. In a previous review of this subject (Abarbanel et al.) RFT was motivated, formulated, and its early results were discussed. These issues are mentioned only briefly in the introduction to the present review in order to make it self-contained. It is then followed by a discussion of the recent developments and progress in the field. A major part of this review is devoted to the discussion of various efforts made to elucidate the s-channel content of Reggeon Field Theory. The formulation of RFT on a lattice and the analysis of production amplitudes are emphasized as the main approaches towards understanding the implication of RFT on s-channel unitarity issues. The path integral and the Hamiltonian formulations of RFT on a lattice, along with their results, are treated in detail. The work done on production amplitudes, in particular cut Reggeon field theory, its derivation and applications, are presented. The probelm of the approach to scaling, the evaluation of the transition energy and scaling functions are discussed as they emerge from the representations of Reggeon Green's functions. Practical problems such as the confrontation of the RFT results with the experimental data and the relevance of different approximations are also analyzed. (Auth.)