Time evolution of the energy density inside a one-dimensional non-static cavity with a vacuum, thermal and a coherent state

We study the time evolution of the energy density for a real massless scalar field in a two-dimensional spacetime, inside an expanding (not oscillating) cavity, and also the force exerted by the field on the moving boundary. Our calculations are based on the exact numerical approach proposed by Cole and Schieve. Considering Neumann and Dirichlet boundary conditions, we investigate the following initial states of the field: vacuum, thermal and the coherent state.