  We investigate cosmological particle production in spacetimes where Lorentz
invariance emerges in the infrared limit, but is explicitly broken in the
ultraviolet regime. Our specific model focuses on the boost subgroup that
supports CPT invariance and results in a momentum-dependent dispersion
relation. Motivated by previous studies on spacetimes emerging from a
microscopic substrate, we show how these modifications naturally lead to
momentum-dependent rainbow metrics. Firstly, we investigate the possibility of
reproducing cosmological particle production in spacetimes emerging from real
Bose gases. We have studied the influence of non-perturbative ultraviolet
corrections in time-dependent analogue spacetimes, leading to
momentum-dependent emergent rainbow spacetimes. Within certain limits the
analogy is sufficiently good to simulate relativistic quantum field theory in
time-dependent classical backgrounds, and the quantum effects are approximately
robust against the model-dependent modifications. Secondly, we analyze how
significantly the particle production process deviates from the common picture.
While very low-energy modes do not see the difference at all, some modes
"re-enter the Hubble horizon" during the inflationary epoch, and extreme
ultraviolet modes are completely insensitive to the expansion.
