We discuss the particle production due to a semitransparent mirror accelerating on the trajectories which simulate the Hawking effect. We find in accordance with a previous result [3] that the number of emitted particles up to infinite times remains finite, but in contrast to the cited paper, we obtain that for large, but finite reflectivities of the mirror, the radiated spectrum is Bose-Einstein and not Fermi-Dirac. We compare the beta coefficients $\beta ({\omega }^{\prime },\omega )$ for the perfectly reflecting and the semitransparency case and point out the differences in the sector of large frequencies ${\omega }^{\prime }$. For the perfect mirror, the source of the infinite number of particles are the frequencies ${\omega }^{\prime }\to \infty$, while for the semitransparent one this contribution is eliminated due to the cutoff effects introduced by the finite barrier energy of the mirror.

• Received 28 August 2008

DOI:https://doi.org/10.1103/PhysRevD.80.125003