Evidence for environment-dependent gravity from galaxies and wide binaries
Year: 2025
Type: article
Abstract: We report empirical evidence that gravity depends not only on local mass but also on the surrounding gravitational environment. Using rotation-curve data from 178 disk galaxies, 1.2 million Solar-neighborhood wide binaries, and 153 strong-lensing systems, we test a new phenomenological law based on an environment-adaptive kernel, (g_taper). The model’s core prediction is an External Field Effect (EFE): a gravitational boost that appears in isolated systems but is screened in strong external fields. This effect is confirmed in wide binaries, where the Milky Way’s field suppresses the boost and yields dynamics consistent with general relativity. Conversely, in low-field dwarf spheroidals, the boost is active and environment-dependent, with Milky Way satellites showing a ~0.6 dex larger gravitational anomaly than Andromeda's. In strong-lensing data, the (g_taper) is preferred over general relativity with a difference in Bayesian Information Criterion (BIC) of 37.7. In independent validation sets, the framework yields a validation negative log-likelihood (NLL) of 5 036, outperforming mond (NLL 679) and general relativity (NLL 118 124). These results demonstrate that an environment-dependent, non-local effect may be a key feature of gravity.
Author: Stålhammar, Gustav
Institution: Karolinska Institutet
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7104014741
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