Phys. Rev. E 99, 031101(R) (2019)

Analogue simulations stir the inner physicist in all of us. It’s almost miraculous that one physical system could be used to simulate and gain insights into another just by virtue of sharing fundamental equations. Yet the approach works — as we know for the case of black-hole analogue systems in fluids and superfluids. But these are not the only objects that can be explored in analogue gravity experiments.

Zack Fifer and colleagues now propose an analogy for the simulation of cosmological scenarios. Their idea is to consider the perturbations at the interface between two immiscible liquids. If the two liquids respond differently to time-varying magnetic fields, with a diamagnetic layer atop a paramagnetic one, the effective gravity felt by the system could be made time dependent. This provides a handle on the perturbation propagation speed — the analogue of the speed of light. Under the right experimental conditions, scale factors can be made to grow exponentially, just as in inflation scenarios, and initial small perturbations would get converted into large-scale structures as happened to our Universe.