Cosmology with higher-derivative matter fields

Abstract

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.

Thick brane models in generalized theories of gravity

“…The modification introduced in the presence of auxiliary fields is more recent [7] and was studied in Refs. [9,10] within the cosmological context, to see how the auxiliary fields may contribute to the cosmic evolution. Moreover, it has also been recently studied within the thick braneworld context, in five dimensions with a single extra dimension of infinite extent [11,12].…”

First-order framework for flat brane with auxiliary fields

“…The modified gravity with nondynamical or auxiliary fields has then been studied in Refs. [4,5] within the cosmological context, to see how the auxiliary fields may contribute to the cosmic evolution. Moreover, it has also been recently studied within the thick braneworld context, in five dimensions with a single extra dimension of infinite extent [6].…”

Matter perturbations in Einstein dark energy model

“…Other generalizations of this idea includes non-minimal coupling between matter energy-momentum tensor and geometry such as f (R, T ) [25][26][27][28][29][30][31][32][33][34][35][36], f (R, T, R μν T μν ) [37,38] gravity theories. Also, one can consider non-standard interactions between matter fields such as f (T, T μν T μν ) theories where T is the trace of energy-momentum tensor [39-41], or derivative matter couplings [42][43][44] where one considers interactions of the form…”