The cosmological frame principle and cosmic acceleration

We discuss implications of the cosmological frame principle which states that cosmological effects of modified gravity must be stable as solutions of each of the corresponding sets of dynamical equations holding in the two conformally-related frames. We show that there are such globally stable, ‘frame-independent’ solutions describing cosmic acceleration, suggesting that they may represent a physically relevant effect. This result highlights the importance of further investigation into the implications of the frame principle for cosmological properties that rely on the use of conformal frames.