Dynamic Equilibrium Theory (DEqT)

Abstract This paper introduces the Dynamic Equilibrium Theory (DET), a unified scalar-tensor framework designed to simultaneously resolve the persistent H0 (Hubble) and S8 (growth) tensions that challenge the ΛCDM cosmological model. We propose a multi-stage evolution of the universe driven by a single scalar field ϕ with an axion-monodromy potential V (ϕ) and a non-minimal conformal coupling Ω(ϕ)R to gravity. An Early Dark Energy (EDE) component, triggered by a thermal phase transition near matter-radiation equality (z ≈ 3400), briefly increases the pre-recombination expansion rate H(z), reducing the comoving sound horizon rs by ∼ 3% and reconciling the locally measured Hubble constant (H0 ≈ 73 km s−1 Mpc−1 ) with CMB data. At late times, the conformal coupling weakens gravity on cosmological scales (Geff < GN ), suppressing structure growth and lowering S8 from ∼ 0.83 to ∼ 0.75, consistent with weak lensing surveys. The model satisfies the cgw = c constraint from GW170817 and includes a Chameleon screening mechanism ensuring consistency with Solar System tests. We derive the full perturbation equations, demonstrate statistical consistency with Planck 2018, DESI 2024, and Pantheon+ datasets, and provide testable predictions for Euclid (2 − 5% deviation in lensing spectrum) and SKA (distinct 21-cm absorption feature at 50 − 100 MHz). Bayesian analysis yields strong evidence (ln B > 5) in favor of DET over ΛCDM