Constraining quantum-gravity predictions for evolving dark energy

Abstract

We confront a class of dark-energy equations of state emerging from group field theory (GFT) quantum gravity with DESI Data Release 2 baryon acoustic oscillations and Pantheon+ type-Ia supernovae. We introduce sampling parametrisations that replace microscopic initial-condition parameters by combinations more directly measured by background probes. The GFT solutions separate into logarithmic, power-law and oscillatory branches, determined by the microscopic interaction parameter $m$. The logarithmic branch is constrained to lie extremely close to a cosmological constant, while the power-law branch permits a small phantom deviation. Without perturbative-theory priors, oscillatory solutions can reproduce the mild preference of the distance data for a dip in $w(z)$ near $z\simeq 0.5$--$1$. Profile-likelihood constraints favour $m\sim -2$ and $m\sim -5$ from BAO and supernovae, shifting towards $m\sim -3.5$ when CMB information is included. Conservative perturbative priors strongly suppress these deviations from $\Lambda$CDM. The quantum-gravity scale $z_q$, related to the average number of quantum gravity atoms, remains unconstrained, although its role in the time evolution makes higher-redshift observations a promising route to probing it. We further find that strong projection effects highlight the importance of performing likelihood profiling alongside our marginal posterior constraints. Our results provide a first direct test of GFT-motivated dynamical dark energy and demonstrate the potential for cosmological observations to inform quantum-gravity model building.

13 pages, 6 figures, 3 tables