We study the geometry and the periodic geodesics of a compact Lorentzian manifold that has a Killing vector field which is timelike somewhere. Using a compactness argument for subgroups of the isometry group, we prove the existence of one timelike non self-intersecting periodic geodesic. If the Killing vector field is never vanishing, then there are at least two distinct periodic geodesics; as ...

The standard text-book Jacobi equation (equation of geodesic deviation) arises by linearizing the geodesic equation around some chosen geodesic, where the linearization is done with respect to the coordinates and the velocities. The generalized Jacobi equation, introduced by Hodgkinson in 1972 and further developed by Mashhoon and others, arises if the linearization is done only with respect to...

We describe a Lorentzian manifold, that is globally hyperbolic and geodesically complete, but such the (minimally coupled) Klein–Gordon operator with standard domain not essentially self-adjoint.

A stationary space-time (M,g) is a 4-manifold M with a smooth Lorentzian metric g, of signature (−,+,+,+), which has a smooth 1-parameter group G ≈ R of isometries whose orbits are time-like curves in M . We assume throughout the paper that M is a chronological space-time, i.e. M admits no closed time-like curves, c.f. §1.1 for further discussion. Let S be the orbit space of the action G. Then ...

We give a functional analytic construction of the fermionic projector on a globally hyperbolic Lorentzian manifold of finite lifetime. The integral kernel of the fermionic projector is represented by a two-point distribution on the manifold. By introducing an ultraviolet regularization, we get to the framework of causal fermion systems. The connection to the “negative-energy solutions” of the D...

The paper deals with twistor spinors on Lorentzian manifolds. In particular , we explain a relation between a certain class of Lorentzian twistor spinors and the Feeerman spaces of strictly pseudoconvex spin manifolds which appear in CR-geometry. Let (M n;k ; g) be a n-dimensional smooth semi-Riemannian spin manifold of index k with the spinor bundle S. There are two conformally covariant diffe...