5.4 Cosmological particle production

Analogue model techniques have also been applied to cosmology. Models considered to date focus on variants of the BEC-inspired analogues:

In all of these models the general expectations of the relativity community have been borne out – the theory definitely predicts particle production, and the very interesting question is the extent to which the formal predictions are going to be modified when working with real systems experimentally [47]. We expect that these analogue models provide us with new insights as to how their inherent modified-dispersion relations affect cosmological processes such as the generation of a primordial spectrum of perturbations (see, for example, [85, 84, 86, 87, 88, 89, 90, 122, 179, 269, 296, 297, 343, 380, 381, 406, 426, 423, 424, 425, 458, 459, 460, 487, 566, 587, 588, 589, 600] where analogue-like ideas are applied to cosmological inflation).

An interesting side-effect of the original investigation, is that birefringence can now be used to model “variable speed of light” (VSL) geometries [58Jump To The Next Citation Point, 181Jump To The Next Citation Point]. Since analogue models quite often lead to two or more “excitation cones”, rather than one, it is quite easy to obtain a bimetric or multi-metric model. If one of these metrics is interpreted as the “gravitational” metric and the other as the “photon” metric, then VSL cosmologies can be given a mathematically well-defined and precise meaning [58, 181].

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