Dynamical Casmir Effect in expanding space?

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The Dynamical Casimir Effect is the production of real photons from the vacuum in a system where one has moving mirrors (see https://www.technologyreview.com/s/424111/first-observation-of-the-dynamical-casimir-effect/). The frequency of the photons is related to the ratio of the velocity v of the mirrors and their separation r.

Could the same phenomenon occur on a cosmological scale in expanding space?

In every region of expanding space we have Hubble's law given by v = H r.

Perhaps real photons are produced with a frequency given by the Hubble parameter H?