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## Section: New Results

### Observability for wave equation and high frequency behavior

Participants: Y. Privat, E. Humbert (Tours University) et E. Trélat (Sorbonne University).

We have determined the asymptotic in time of the observability constant in closed manifolds. In particular, we have proved that this limit can be represented as the minimum of two quantities: one purely spectral and another called the geometric quantity representing the limit of the average time spent by geodesics within the observation domain [19]-[19].