In the last few years there has been a revival of interest in the old idea that spacetime may have more than four dimensions, all but four having been curled up into a small circumference. In this view the various particles and interactions we see at ordinary energies arise from a simple, perhaps purely geometrical, theory in higher dimensions. This idea has profound implications for elementary particle physics and cosmology, and raises challenging problems of mathematics. These matters were the topic of the Second Jerusalem Winter School of Theoretical Physics.Contents:

• Some Aspects of Homotopy and De Rham Theory (R Bott)
• Recent Results in Extra Dimensions (M J Duff)
• Lectures on Superstring Theory (J H Schwarz)
• Elementary Differential Geometry from a Generalized Standpoint (S Weinberg)
• Fermion Chirality from Higher Dimensions and Kaluza–Klein Theories with Non-Compact Internal Space (C Wetterich)

Readership: High energy physicists and cosmologists.