Cosmology in new gravitational scalar-tensor theories

Understand

We investigate the cosmological applications of new gravitational scalar-tensor theories, which are novel modifications of gravity possessing 2+2 propagating degrees of freedom, arising from a Lagrangian that includes the Ricci scalar and its first and second derivatives.

• Extracting the field equations we obtain an effective dark energy sector that consists of both extra scalar degrees of freedom, and we determine various observables.
• We analyze two specific models and we obtain a cosmological behavior in agreement with observations, i.e.
• transition from matter to dark energy era, with the onset of cosmic acceleration.