Cosmology with higher-derivative matter fields

TL;DR

This paper explores a new class of modified gravity theories with higher-derivative matter fields, leading to diverse cosmological behaviors including acceleration and various dark energy regimes, potentially distinguishable from other models.

Contribution

It introduces a novel modified gravity framework with higher derivatives of matter fields and analyzes its cosmological implications across different matter types.

Findings

Accelerating and de Sitter phases identified.

Dark energy equation-of-state varies from quintessence to phantom.

Distinct signatures may differentiate this model from other modified gravity theories.

Abstract

We investigate the cosmological implications of a new class of modified gravity, where the field equations generically include higher-order derivatives of the matter fields, arising from the introduction of non-dynamical auxiliary fields in the action. Imposing a flat, homogeneous and isotropic geometry we extract the Friedmann equations, obtaining an effective dark-energy sector containing higher derivatives of the matter energy density and pressure. For the cases of dust, radiation, and stiff matter we analyze the cosmological behavior, finding accelerating, de Sitter, and non-accelerating phases, dominated by matter or dark energy. Additionally, the effective dark-energy equation-of-state parameter can be quintessence-like, cosmological-constant-like, or even phantom-like. The detailed study of these scenarios may provide signatures that could distinguish them from other candidates of modified gravity.