Table of contents

Time variation of the fundamental constants is one manifestation of the violation of Einstein's Equivalence Principle required by theories uniting gravitation with the strong and electroweak interactions.

The rapid progress in the development of atomic frequency standards based on optical transitions is leading to ever more stringent constraints on time variation of the fine structure constant, α, which is the coupling constant of the electromagnetic interaction, and to quantities such as nuclear g-factors and mass ratios, which depend on the strong interaction. Absolute frequency measurements of these optical frequency standards currently place a limit on present-day time variation of the fine structure constant of (−4 ± 4) parts in 10¹⁶ per year. There are good prospects for an improvement of two orders of magnitude in this limit by means of direct frequency comparisons between optical frequency standards.

The nuclear structure in regions of the Segré chart which are of astrophysical importance is reviewed. The main emphasis is put on those nuclei that are relevant for stellar nucleosynthesis in fusion processes, and in slow neutron capture, both located close to stability, rapid neutron capture close to the neutron dripline and rapid proton capture near the proton dripline. The basic features of modern nuclear structure, their importance and future potential for astrophysics and their level of predictibility are critically discussed. Recent experimental and theoretical results for shell evolution far off the stability line and consequences for weak interaction processes, proton and neutron capture are reviewed.