This volume contains written versions of the lectures given at the CXXXII Course of the Enrico Fermi School of Physics on the subject of Dark Matter in the Universe, held in Varenna at Villa Monastero 25 July-4 August 1995.

Physics and astrophysics came to dark matter through many different routes, finally accepting it, but often with some distaste. It has been noticed that the existence of dark matter is yet another displacement of humans from the centre of the Universe: Not only do our planet and our sun have no central position in the Universe, not only are humans just animals (although with a “specialized” central nervous system), but even the material of which we are made is only a marginal component of the cosmic substance! If this is the right attitude to take, scientists feeling distaste for dark matter are much like Galileo Galilei's colleagues who refused to look through the telescope to watch the Medicei planets.

Nevertheless, astronomers, when requested to take a ballot in favour of some cosmological model, often still vote for “pure baryonic” with substantial majorities, although most cosmologists assume that a “cold” component of dark matter plays a role in producing the world as we observe it.

One of the aims of this school was to push the new generation to take a serious attitude in ballots-no doubt a major problem not only in science. Therefore, dark matter, as is indicated by the name of the course, is the central topic of its lectures, and the lecturers review most of the evidence leading to it. Their lectures show that the data accumulating in laboratories and observatories are already sufficiently advanced to begin to allow discrimination among different kinds of dark-matter models. Further, the lecturers debate what can be origin of dark matter and whether “cold” dark matter is enough.

The course was organized with the aim of giving a comprehensive overview of recent developments in theoretical and observational cosmology. Among the many subjects covered, particular emphasis was given to 1) summarizing the current status of the observations both of the distribution of the nearby galaxies and of the evolution of more distant galaxies; 2) advanced statistical techniques for quantifying structure in galaxy redshift and peculiar-velocity surveys; 3) the art of cosmic inflation and models for dark-matter candidates, and their implications for cosmic-microwave-background observations; 4) implications of cold-dark-matter variants for large-scale structure, as worked out both by quasi-linear techniques and by fully nonlinear simulations; and 5) Eulerian and Lagrangian approximations for treating the nonlinear dynamics. We were fortunate to have had as lecturers many of the leading experts on all of these topics, and we are grateful to them both for their excellent lectures and for writing them up quickly. We are also grateful to the students for their enthusiastic participation.

We want to express our gratitude also to the Italian Physical Society for its support of the school in many ways, and in particular to E. Mazzi and her staff for their invaluable help during the school.

S. Bonometto

J.R. Primack

A. Provenzale