Title: On a Problem of Osserman in Lorentzian Geometry

Author:  E. Garcia-Rio, D.N. Kupeli and M.E. Vazquez-Abal

Notes: 17 pages, to appear in Differential Geometry and its Applications

Abstract:
          A problem of Osserman on the constancy of the eigenvalues of the
Jacobi operator is studied in Lorentzian geometry. Attention is paid to the
different cases of timelike, spacelike and null Osserman condition. One also
shows a relation between the null Osserman condition and a previous one on
infinitesimal null isotropy.

Keywords:  Osserman conjecture, Lorentz manifold, Jacobi operator, 
infinitesimal isotropy, warped product.

M.S. classification:  53B30, 53C50.