Could Einstein's equations explain cosmic expansion without dark energy?

Researchers from UC Davis have proposed that dark energy may not be necessary to explain the universe's acceleration. They found weak points in the Lambda-cold dark matter model using Einstein's equations. By examining instabilities in Friedmann spacetimes, they suggest alternative explanations for cosmic expansion. Their work raises questions about the Copernican principle in the context of current models. This research could lead to significant shifts in our understanding of cosmology.