  The recently proposed states of low energy provide a well-motivated class of
reference states for the quantized linear scalar field on cosmological
Friedmann-Robertson-Walker spacetimes. The low energy property of a state is
localized close to some value of the cosmological time coordinate. We present
calculations of the relative cosmological particle production between a state
of low energy at early time and another such state at later time. In an
exponentially expanding Universe, we find that the particle production shows
oscillations in the spatial frequency modes. The basis of the method for
calculating the relative particle production is completely rigorous.
Approximations are only used at the level of numerical calculation.
