Since the second half of the 20th century, the Riemannian and semi-Riemannian geometries have been active areas of research in di?erential geometry and its - plications to a variety of subjects in mathematics and physics. A recent survey in Marcel Berger s book 60] includes the major developments of Riemannian ge- etry since 1950, citing the works of di?erential geometers of that time. During the mid 1970s, the interest shifted towards Lorentzian geometry, the mathematical theory used in general relativity. Since then there has been an amazing leap in the depth of the connection between...
Since the second half of the 20th century, the Riemannian and semi-Riemannian geometries have been active areas of research in di?erential geometry an...
