Generalized energy conditions in Extended Theories of Gravity

Understand

Theories of physics can be considered viable if the initial value problem and the energy conditions are formulated self-consistently.

• The former allow a uniquely determined dynamical evolution of the system, and the latter guarantee that causality is preserved and that "plausible" physical sources have been considered.
• In this work, we consider the further degrees of freedom related to curvature invariants and scalar fields in Extended Theories of Gravity (ETG).
• These new degrees of freedom can be recast as effective perfect fluids that carry different meanings with respect to the standard matter fluids generally adopted as sources of the field equations.