Catherine Sulem
Department of Mathematics, University of Toronto
Bloch theory and spectral gaps for linearized water waves
We consider the movement of a free surface of a two-dimensional fluid over a variable听bottom. We assume that the bottom has a periodic prole and we study the water wave听system linearized near a stationary state. The latter reduces to a spectral problem for the听Dirichlet{Neumann operator in a fluid domain with a periodic bottom and a at surface听elevation. Bloch spectral decomposition is a classical tool to address problems in periodic听geometries or equivalently differential operators with periodic coefficients. We show that听the spectral problem admits a Bloch decomposition in terms of spectral band functionsand their associated band-parametrized eigenfunctions. We find that, generically, the听spectrum consists of a series of bands separated by spectral gaps which are zones offorbidden energies.
听
听