Is DESI Seeing Dynamical Dark Energy, or a Cosmic Glitch in Gravity?

Combined baryon acoustic oscillation (BAO) and cosmic microwave background (CMB) data have begun to mildly favor departures from ΛCDM, and these hints are usually interpreted as two-parameter dynamical dark energy. The preprint examines an alternative explanation: a one-parameter 'cosmic glitch in gravity' model in which the cosmological gravitational coupling differs from Newton's constant, as in Hořava gravity.

Using Planck+ACT+SPT CMB data and DESI DR2 BAO data, the analysis finds G_cosmo/G_N = 0.9920 ± 0.0025, a 3.3σ preference for weaker cosmological gravity. The result is robust to adding CMB lensing and supernova data.

The glitch model also has a predictive advantage: when fitted to the CMB alone, it predicts the DESI distances, whereas w0waCDM does not. The abstract therefore argues that the DESI hints need not imply dynamical dark energy, since a one-parameter modification of gravity fits at least as well.