Study suggests cosmic acceleration may not require dark energy
Mathematicians say instabilities in conventional cosmological models could offer an alternative explanation, but their findings still need testing against observations.
Researchers at the University of California, Davis, say their mathematical study suggests Einstein’s equations could account for the universe’s accelerating expansion without dark energy. Published in Proceedings of the Royal Society A, the work questions the stability of the mathematical framework underlying the prevailing Lambda-cold dark matter model.
The team examined the Einstein-Euler equations, which link general relativity with the behavior of fluids. Their calculations indicate that Friedmann spacetimes, used to describe cosmic expansion, are unstable under certain disturbances. Corresponding author Blake Temple, a distinguished professor emeritus of mathematics at UC Davis, said disturbances varying with distance from a central point can grow on large scales rather than subside.
The researchers argue that this instability could produce accelerated expansion without introducing a cosmological constant or dark energy. Their framework allows behavior close to conventional predictions near a center of symmetry, while expansion farther from that center can depart from those predictions. The presence of a center also raises questions about where observers would have to be for the model to fit observations.
The findings are theoretical, not observational evidence that dark energy is unnecessary. Whether the proposed explanation describes the actual universe depends on how its predictions compare with astronomical observations.
