• Accepted Paper

Cosmographic reconstruction of the quintessence potential in scalar-tensor gravity

G. Antonopoulos and L. Perivolaropoulos

Phys. Rev. D - Accepted 3 November, 2026

DOI: https://doi.org/10.1103/pwq9-kn5k

Abstract

We generalise the cosmographic reconstruction programme of Chakraborty, Dunsby & Scherrer to scalar-tensor gravity. Working in the Jordan frame with a general non-minimal coupling F(Φ), we derive exact closed-form expressions for the potential slope λU, the coupling slope λF, and their curvature parameters ΓU and ΓF in terms of the cosmographic parameters (q,j,s), the Planck-mass running αM=dlnF/dlna and its derivatives. We express αM and its derivatives in terms of a set of coefficients gn describing the time variation of the gravitational constant G∝F−1, casting all four quantities in terms of the time derivatives of G, which are in principle observable. We then evaluate the reconstruction against current data, including DESI DR2 baryon acoustic oscillation measurements and Solar-System tests of gravity, propagating the cosmographic uncertainties through to the reconstructed potential. All expressions reduce analytically to those of Chakraborty, Dunsby & Scherrer in the minimally-coupled limit, which we verify symbolically. We find that the potential slope λU is recovered at the few-tenths level while the curvature ΓU is essentially unconstrained. We further show that for minimally-coupled quintessence the positivity of the scalar kinetic term is equivalent to $w_{\rm eff,0}\geq-1$, so that the region of cosmographic parameter space closed to it is exactly the phantom region, and that the non-minimal coupling reopens this region through a single coefficient g2 of the gravitational tower. Because Solar-System tests restrict |g1|≲10−3 at our benchmarks while the reconstruction is sensitive to g2∼𝒪(0.1), the framework presupposes that αM is passing through zero at the present epoch, as expected on the Damour–Nordtvedt least-coupling attractor.

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