Analog of cosmological particle creation in electromagnetic waveguides

We consider an electromagnetic waveguide with a time-dependent propagation speed v(t) as an analog for cosmological particle creation. In contrast to most previous studies which focus on the number of particles produced, we calculate the corresponding two-point correlation function. For a small steplike variation delta v(t), this correlator displays characteristic signatures of particle pair creation. As another potential advantage, this observable is of first order in the perturbation delta v(t), whereas the particle number is second order in delta v(t) and thus more strongly suppressed for small delta v(t).