A new mechanism for neutralizing the cosmological constant

Abstract

We propose a dynamical mechanism for neutralizing the cosmological constant in our universe. The analysis is wholly lorentzian, unlike most other mechanisms which rely on the problematic euclidean quantum gravity. Additionally, we do not have to assume any properties of a complete quantum gravity theory for our result. Quantum cosmology is an effective theory below the Planck scale, and it suffices for the purpose of our demonstration. The vacuum energy from particle physics is many orders of magnitude too great to explain the measured smallness of the cosmological constant. Any generic field that allows us to shift the vacuum energy has the possibility of neutralizing it. However, such a field has an infinity of possible vacuum states, and we have to be in exactly the right one to achieve the cancellation. We show that when we third quantize a cosmology containing such a field in its particle physics sector we do have the possibility of selecting one vacuum over another. (The field we use for the sake of demonstration is a four-form.) The essential result of our paper is that the dominant vacuum state for the field is indeed the one that exactly cancels the particle physics vacuum energy. This means that a large universe, such as ours, has a vanishing cosmological constant.