This article concerns the exact controllability of unitary groups on Hilbert spaces with unbounded control operator. It provides a necessary and sufficient condition not involving time which blends aâ€¦ (More)

In this paper, the null controllability in any positive time T of the first-order equation (1) Ë™ x(t) = e iÎ¸ Ax(t) + Bu(t) (|Î¸| < Ï€/2 fixed) is deduced from the null controllability in some positiveâ€¦ (More)

This paper generalizes and simplifies abstract results of Miller and Seidman on the cost of fast control/observation. It deduces final-observability of an evolution semigroup from some stationaryâ€¦ (More)

A self-adjoint operator A and an operator C bounded from the domain D(A) with the graph norm to another Hilbert space are considered. The admissibility or the exact observability in finite time ofâ€¦ (More)

Given a time T > 0 and a region â„¦ on a compact Riemannian man-ifold M , we consider the best constant, denoted C T,â„¦ , in the observation inequality for the SchrÃ¶dinger evolution group of theâ€¦ (More)

For all sums of eigenfunctions of a semiclassical SchrÃ¶dinger operator below some given energy level, this paper proves that the ratio of the L norm on R over the L norm on any given open set isâ€¦ (More)