Limits of the Rastall--Einstein Equivalence: Matter-Action Compatibility, FLRW Dynamics, and Exceptional Sectors
The discussion of the paper "Limits of the Rastall—Einstein Equivalence" explores how theoretical mathematical equivalence between different gravity models relates to their physical reality. The authors demonstrate that while models may be algebraically identical, they are tested against real matter in an expanding universe (FLRW dynamics). The hosts conclude that physical testing requires understanding how specific matter types react to the derived effective gravitational coupling.