Particle creation via high frequency dispersion

We investigate the particle creation caused by a nonlinear dispersion relation for a massless scalar field propagating on a background curved spacetime in two dimensions. The dispersion relation adopted agrees with the standard dispersion relation at long wavelengths but is modified at short wavelengths, the division being characterized by a new length scale 1/k₀. We consider both spacetimes with and without a black hole. Those without contain instead a uniformly moving ``bump.'' The black hole cases considered have Hawking temperatures TH>k₀/100. We find that the particle creation arises in all cases from two effects: scattering and mode conversion. The latter was identified by Corley and Jacobson as the phenomenon responsible for the Hawking effect.