Physicists Find Possible Errors In 100-Year-Old Model of the Universe

A trio of preprint papers suggests the universe may not be perfectly uniform on the largest scales, finding tentative 2-to-4-sigma deviations from a core assumption of standard cosmology known as FLRW geometry. Live Science reports: The work combines observations of distant exploding stars and large-scale galaxy surveys to probe whether the universe truly follows a nearly 100-year-old mathematical framework known as Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology. The analyses revealed mild-but-intriguing deviations from the predictions of the standard model. "We saw a surprising violation of an FLRW curvature consistency test, hinting at new physics beyond the standard model," study co-author Asta Heinesen, a physicist at the Niels Bohr Institute in Copenhagen and Queen Mary University in London, told Live Science via email, referring to the assumption that the space's curvature is the same everywhere. "This could potentially be due to various effects, but more research is needed to address the cause of the FLRW violation that we see empirically." [...] The analyses revealed small but potentially important departures from the predictions of standard FLRW cosmology. Depending on the dataset and analysis method, the discrepancy reached a statistical significance of about 2 to 4 sigma. In physics, sigma measures how likely a result is to arise purely by chance; a 5-sigma result is typically required before scientists claim a discovery, so the new findings remain tentative. Still, the results suggest that something unexpected may be affecting the geometry or expansion of the universe. "The main finding is that you can directly measure Dyer-Roeder and backreaction effects from available cosmological data, and clearly distinguish these effects from other alterations of the standard cosmological model, such as evolving dark energy and modified gravity theories," Heinesen said. "This was previously not possible in such a direct way, and this is what I think is the breakthrough in our work." "If these indicated deviations from an FLRW geometry are real, it would signify that most of the cosmological solutions considered for solving the cosmological tensions -- evolving or interacting dark energy, new types of matter or energy, modified gravity and related ideas within the FLRW framework -- are ruled out," the researchers wrote. The next step will involve applying the new theoretical framework to larger and more precise datasets. "It is to apply our theoretical results to data to test the standard model and to produce constraints on the Dyer-Roeder and backreaction effects," Heinesen said.

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