  Quantum particle creation from spacetime horizons, or accelerating boundaries
in the dynamical Casimir effect, can have an equilibrium, or thermal,
distribution. Using an accelerating boundary in flat spacetime (moving mirror),
we investigate the production of thermal energy flux despite non-equilibrium
accelerations, the evolution between equilibrium states, and the "interference"
between horizons. In particular, this allows us to give a complete solution to
the particle spectrum of the accelerated boundary correspondence with
Schwarzschild-de Sitter spacetime.
