Dynamical aspects for scalar fields coupled to cubic contractions of the Riemann tensor

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The paper studies a new type of dark energy, a scalar field with positive or negative kinetic energy, generically coupled to a term which is composed by specific contractions of the Riemann tensor.

• After presenting the resulting field equations, we have analyzed the physical characteristics of the corresponding model by implementing the linear stability theory.
• In the case of an exponential coupling function and exponential potential energy we have deduced the phase space characteristics, analyzing the critical points obtained which can represent specific eras in the evolution of the Universe.
• The analytical study is showing that this model can represent a feasible cosmological setup, having various epochs which correspond to stiff-fluid, matter domination, and dark energy eras, pointing towards the emergence of the accelerated expansion as a geometrical effect.