Cosmological dynamics of interacting dark matter-dark energy in generalized Rastall gravity

Gonzalez-Espinoza M.; Herrera R.; Otalora G.; Ríos-Morales C.; Rodriguez-Benites C. · Nuclear Physics B (2026) · DOI: 10.1016/j.nuclphysb.2026.117563

Resumen

In this work, we investigate late-time interacting cosmologies within the framework of generalized Rastall gravity, where the interaction arises naturally from the non-conservation of the energy-momentum tensor. We formulate the background evolution of the dark sector as an autonomous dynamical system, defining interaction terms Q1=αf˙ and Q2=−f˙(1+α), with α a constant parameter and f a time-dependent function. Three interaction scenarios are studied: f ∝ ρm, f ∝ ρde , and f∝ρm+ρde, assuming a constant dark-energy equation-of-state parameter wde . For each scenario, we derive the closed dynamical system in terms of the density parameters (Ω de , Ω m ), identify its fixed points, and analyze their stability across the parameter space. In this context, the phase space exhibits standard cosmological dynamics: an unstable radiation point, a transient matter saddle, and a stable late-time attractor with accelerated expansion. In addition, we perform a joint likelihood analysis using Cosmic Chronometers, PantheonPlus, and DESI data to obtain marginalized parameter estimates at the 68% and 95% confidence levels, constraining the parameter space in each interaction model.

Instituciones: Universidad Nacional de Trujillo