Global Waves with Non-Positive Energy in General Relativity

2000 Mathematics Subject Classification: 35Lxx, 35Pxx, 81Uxx, 83Cxx.

Local Energy Decay in Even Dimensions for the Wave Equation with a Time-Periodic Non-Trapping Metric and Applications to Strichartz Estimates

2000 Mathematics Subject Classification: 35B40, 35L15.

On the Isoenergetical Non-Degeneracy of the Problem of two Centers of Gravitation

* Partialy supported by contract MM 523/95 with Ministry of Science and Technologies of Republic of Bulgaria.