Energy Radiation from a Moving Mirror with Finite Mass

In this paper we study energy radiation from a moving mirror in 1+1 dimensional space-time. The mirror is assumed to have finite mass and accordingly to receive back reaction from scalar photon field. The mode expansion of the scalar field becomes different from that without back reaction though the trajectory of the mirror is not changed. Then energy density of the vacuum becomes to have finite value proportional to square of the mass of the mirror. Moreover we compute the energy momentum tensor of the radiation in the case that acceleration of the mirror is small. As a result we show that the mirror creates energy radiation whose quantity does not depend on its mass but on its acceleration even if the acceleration is uniform.