Future Dark Energy Constraints from Atomic Clocks

TL;DR

The paper investigates whether atomic clocks and Lunar Laser Ranging can tightly constrain scalar-tensor dark energy in the Solar System. By linking clock frequency drifts to the scalar field dynamics and combining with LLR and PPN bounds, it derives a central relation that constrains the present-day dark energy equation of state, pushing viable models toward ultra-slow-roll near a cosmological constant. The analysis shows that canonical and many non-canonical scalar-tensor theories are effectively indistinguishable from ΛCDM at z ~ 0, ruling out broad classes of dynamical gravity scenarios. These Solar System tests thus provide powerful, model-independent constraints on late-time dark energy and guide future precision clock experiments and space-based clock networks.

Abstract

We show that atomic clock measurements provides an exceptionally sensitive Solar System probe of scalar tensor dark energy. By connecting variations in Newton's constant and differential clock drifts to the dynamics of a single dark energy scalar, we derive a direct constraint on the present day equation of state and our results force any locally coupled scalar dark energy into a very slowly rolling regime, giving the strongest bounds on the equation of state parameter. This is independent of potential shape or kinetic structure and rules out broad classes of canonical and non canonical models, leaving only near Lambda CDM behavior or fully decoupled fields as viable late time scalar dark energy, thereby leaving cosmological constant and minimally coupled scalar field models as the most consistent dark energy regimes. We also use results from Lunar Laser Ranging and photon trajectories to further strengthen our the depth of our constraints.