Scalar particle production by gravitational waves

Abstract

We compute the expected number of particles generated by a plane gravitational wave, and show that it is possible for such a wave to generate particles out of the vacuum. We compute this number both classically and using canonical quantization. The normal procedure for canonical quantization states that the field and its conjugate momentum commute, which is not possible. We show two ways one can change this approach to produce results consistent with the classical analysis. However, the plane wave we use gives infinite particle creation density. This result is probably due to a plane gravitational wave spanning all of space not being physically possible. We suggest how the latter can be fixed, which would make it possible to compute the particle creation number for a realistic wave.