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Paradigm Challenge  /  Space

Our local patch of the universe is about ten percent more curved than the rest of the cosmos, throwing a wrench into our standard model of space.

Cosmologists usually assume the universe is perfectly smooth and expands at the same rate everywhere. Direct measurements of our local neighborhood out to three hundred megaparsecs show that this smooth assumption is wrong. Spatial curvature accounts for a significant chunk of the local energy budget that is not present in global models. This means the expansion rate we measure from Earth might be a local fluke rather than a universal constant. If our neighborhood is special, we may have to rethink the entire history of the Big Bang and dark energy. It essentially means we are living in a cosmic bubble that does not match the rest of the map.

Original Paper

Backreaction and the Role of Spatial Curvature in the Cosmic Neighborhood

Marco Galoppo, Thomas Buchert, Pierre Mourier

arXiv  ·  2605.05454

We present the first direct computation of spatially averaged dynamical quantities in the local Universe, employing the Cosmicflows-4++ reconstruction and a covariant scalar averaging formalism. We extract the domain-averaged density, expansion rate, spatial curvature, and kinematical backreaction over cosmologically relevant domains around our Galaxy, extending up to a comoving radius of $300~\mathrm{Mpc}/h$. The resulting domain-averaged present-day energy budget features nontrivial variations