Clare tells us about how chameleon dark energy models can be very tightly constrained by simple atomic lab experiments (well, simple compared to particle accelerators and space telescopes).

Chameleon models were popular for dark energy because their non-linear potentials generically create screening mechanisms, which stop them generating a “fifth force” even though they couple to matter. This means we wouldn’t normally see their effects on Earth. However, in a suitably precise atomic experiment the screening can be minimised and their effect measured.

In less than five years, Clare and her collaborators went from the idea to the completed experiment, which rules out almost all of the viable parameter space where a chameleon model can explain dark energy. Only a tiny sliver of allowed space is left, albeit at fundamental parameter values that would be natural ones – so maybe the chameleon is hiding right there waiting?

Most relevant paper: https://arxiv.org/abs/1812.08244
Clare: https://www.nottingham.ac.uk/physics/people/clare.burrage