The idea that most of our Universe consists of unknown forms of matter and energy is disturbing. But with observational evidence gathering — notably the Dark Energy Survey data release last month — this uncomfortable scenario is becoming more convincing. Dark matter and dark energy can be incorporated in the current cosmological working model, the lambda cold dark matter (ΛCDM) model. The accelerated expansion of the Universe, driven by dark energy, is accounted for by the cosmological constant Λ. But this is not hassle free: there are discrepancies between the parameters of ΛCDM derived from the cosmic microwave background and other cosmological measurements.
Gong-Bo Zhao and colleagues have suggested a way to relieve these tensions: consider a dynamical dark energy model in which Λ is a function of the redshift. Using statistical tests, they analysed the tensions between datasets from different sources and found that that dynamical dark energy is slightly favoured over ΛCDM. It is, of course, too early to draw any definitive conclusions, but upcoming observations will hopefully settle the nature of the cosmological constant.
Rights and permissions
About this article
Cite this article
Georgescu, I. A changing constant?. Nature Phys 13, 824 (2017). https://doi.org/10.1038/nphys4261