Einstein–Cartan and general relativity cosmologies with a nonminimally coupled ghost scalar field

Abstract

Exact general solutions for spatially flat isotropic and homogeneous cosmologies with a nonminimally coupled ghost scalar field that has polynomial potentials of the fourth degree are obtained in the framework of the Einstein–Cartan theory (ECT) and general relativity (GR). The special values of coupling constant \(\xi \) and restrictions on \(\xi \) are found for the above solutions. Some effects of torsion and scalar field potential are elucidated. It is shown that solutions can describe the bouncing models with the late-time accelerated expansion. It is demonstrated that some models admit the unified scenario for dark matter and dark energy: (i) both singular models in ECT with a de Sitter-like asymptotic and with the power-law \((t^{4/3})\) asymptotic at late times, (ii) singular and nonsingular models in GR with a de Sitter-like asymptotic at late times.