Late-Transition Interacting Thawer Dark Energy: Model Definition and Benchmark Consistency Tests

Abstract

We formulate the late-transition interacting thawer (LTIT) as a late-activating, variable-coupling realization of coupled quintessence in which a canonical scalar field couples conformally only to cold dark matter. The construction is a non-universal dark-sector interaction: baryons and radiation remain minimally coupled, while CDM follows a conformally related metric. This structure ties three observational sectors to one microscopic mechanism--the pre-recombination calibration scale, the low-redshift expansion history, and the coupled growth response. We derive the exact background equations, the exact CDM scaling identity $\rhoc(a)=ρ_{c0}a^{-3}C[ϕ(a)]/C(ϕ_0)$, and the coupled CDM--scalar perturbation equations in synchronous gauge in a form suitable for Einstein--Boltzmann solvers. In the representative benchmarks, $\hat{I}{\text{c◯}}_{\ddot{I}}•(z_{\ast })\sim 10^{-9}$, $|\hat{I}”r_d/r_d|\le 3.82\times 10^{-3}$, and ${\max }_{0<z<3}|E/E_{\hat{I}›\mathrm{CDM}}-1|\le 0.380\%$, while the quasi-static growth indicator ranges from $0.725\%$ to $5.94\%$. LTIT therefore demonstrates how late activation can preserve the early calibration sector while producing a perturbation-sensitive signature, providing a concrete target for Boltzmann-level tests of interacting dark energy.

10 pages, 3 figures, 2 tables

References in corpus (1)

• Dark Energy After DESI DR2: Observational Status, Reconstructions, and Physical Models