Following the lines of the celebrated Riemannian result of Gromoll and Meyer, we use infinite dimensional equivariant Morse theory to establish the existence of infinitely many geometrically distinct closed geodesics in a class of globally hyperbolic stationary Lorentzian manifolds
On a Gromoll-Meyer type theorem in globally hyperbolic stationary spacetimes / BILIOTTI L.; MERCURI F; PICCIONE P. - In: COMMUNICATIONS IN ANALYSIS AND GEOMETRY. - ISSN 1019-8385. - 16(2008), pp. 333-393.