Cosmic Acceleration as the Solution to the Cosmological Constant Problem

Abstract

In this paper we provide both a diagnosis and resolution of the cosmological constant problem, one in which a large (as opposed to a small) cosmological constant Λ can be made compatible with observation. We trace the origin of the cosmological constant problem to the assumption that the local gravitational Newton constant G (as measured in a Cavendish experiment) sets the scale for global cosmology. Then we show that once this assumption is relaxed, the very same cosmic acceleration that has served to make the cosmological constant problem so very severe can instead serve to provide us with its potential resolution. In particular, we present an alternate cosmology, one based on conformal gravity, a theory whose effective cosmological G_eff not only differs from the Cavendish one by being altogether smaller than it but, by even being explicitly negative, naturally leads to cosmological repulsion. We show in the conformal theory that once given only that the sign of Λ is specifically the negative one associated with spontaneous scale symmetry breaking, then that alone, no matter how big Λ might actually be in magnitude, is not only sufficient to make the actually measurable contribution 8πG_effΛ/3cH²(t₀) of Λ to current era cosmology naturally be of order 1 today, but to even do so in a way that is fully compatible with the recent high-z supernova cosmology data. Thus, to solve the cosmological constant problem, we do not need to change or quench the energy content of the universe, but rather we only need to change its effect on cosmic evolution.