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Junichi Mukuno

2012-03-19
16:20:00 - 17:10:00

308 , Mathematics Research Center Building (ori. New Math. Bldg.)

In 1962, E. Calabi and L. Markus observed that there is no infinite subgroups of the Lorentz group $O(n+1,1)$ whose left actions on the de Sitter space $O(n+1.1)/O(n,1)$ is properly discontinuous. The observation of E. Calabi and L. Markus was generalized to a certain class of homogeneous spaces by J. A. Wolf, R. S. Kulkarni, and T. Kobayashi. In this talk, we provide a new extension of the observation of E. Calabi and L. Markus to some class of Lorentzian manifolds that are not necessarily homogeneous by using the techniques of differential geometry.