THE STRUCTURES OF SPACETIME GEOMETRY
We shall here review some of the insights about the structures of geometry of spacetime implied by gravitational physics. In the early 70s Jürgen Ehlers (1929–2008), Felix A. E. Pirani and Alfred Schild (1921–1977) proposed an interpretational framework for relativistic theories, which suggests to revise thestructure of gravitational theories. We shall review a proposal for classifying extended theories of gravitation and consider some examples and applications.
More...