Gravity Initiative Lunch

I discuss the possibility that the ''dark energy'' that drives the accelerated expansion of the universe arises not from a conventional cosmological constant term in the gravitational action, but rather from a frame-dependent but Weyl scaling invariant action term. This action mimics the standard cosmological action in an unperturbed Friedmann-Robertson-Walker (FRW) cosmology, but has novel consequences both for black hole horizons and, the focus of this talk, for perturbations around the FRW solution. I discuss motivations for a Weyl invariant cosmological action, new insights it would give on old problems, and implications for the recently much discussed ''Hubble Tension''. The talk keeps technicalities to a minimum, requiring only a basic knowledge of FRW cosmology and ordinary differential equations, and concludes with a list of problems for further study, some of which could be undergraduate paper or thesis topics.