This is a collection of important papers presented by an international group of outstanding scientists at a seminar on strings and symmetries held in Stony Brook. This volume contains reviews on modern string theory and particle physics, including supersymmetric quantization, supergravity, conformal field theory, topological field theory, string phenomenology, matrix models, and W gravity. This proceedings is both an excellent introduction as well as reference source for researchers.

W-symmetry is an extension of conformal symmetry in two dimensions. Since its introduction in 1985, W-symmetry has become one of the central notions in the study of two-dimensional conformal field theory. The mathematical structures that underlie W-symmetry are so-called W-algebras, which are higher-spin extensions of the Virasoro algebra. This book contains a collection of papers on W-symmetry, covering the period from 1985 through 1993. Its main focus is the construction of W-algebras and their representation theory. A recurrent theme is the intimate connection between W-algebras and affine Lie algebras. Some of the applications, in particular W-gravity, are also covered.The significance of this reprint volume is that there are no textbooks entirely devoted to the subject.

These proceedings cover the most recent advances in these topics keeping in mind their impact on observable phenomena. In addition they review the status and prospects of all known gauge forces, including the experimental results on their validity.

The areas covered in this volume include: duality in string theory and supersymmetric gauge theories; phenomenological applications of string theory; strings in curved spacetime; quantum gravity; SUSY conformal field theories; QCD strings; aspects of mathematical physics, including: mirror symmetry, W-algebras, representation theory.

The contemporary trends in the quantum unification of all interactions including gravity motivate this Course. The main goal and impact of modern string theory is to provide a consistent quantum theory of gravity. This, Course is intended to provide an updated understanding of the last developments and current problems of string theory in connection with gravity and the physics at the Planck energy scale. It is also the aim of this Course to discuss fundamental problems of quantum gravity in the present-day context irrespective of strings or any other models. Emphasis is given to the mutual impact of string theory, gravity and cosmology, within a deep a well defined programme, which provides, in addition, a careful interdisciplinarity. Since the most relevant new physics provided by strings concerns the quantization of gravity, we must, at least, understand string quantization in curved space-times to start. Curved space-times, besides their evident relevance m classical gravitation, are also important at energies of the order of the Planck scale. At the Planck energy, gravitational interactions are at least as important as the rest and can not be neglected anymore. Special care is taken here to provide the grounds of the different lines of research in competition (not just only one approach); this provides an excellent opportunity to learn about the real state of the discipline, and to learn it in a critical way.