3 Cosmological Constant Problem

The cosmological constant problem is reviewed and a possible quantum gravity resolution is proposed. A space satellite Eötvös experiment for zero-point vacuum energy is proposed to see whether Casimir vacuum energy falls in a gravitational field at the same rate as ordinary matter. 1 Cosmological Constant Problem • It is generally agreed that the cosmological constant problem (CCP) is one of the most severe problems facing modern particle and gravitational physics. It is believed that its solution could significantly alter our understanding of particle physics and cosmology [1]. • The accelerating universe and dark energy. Is the cosmological constant the explanation for the accelerating universe? What is dark energy? • There have been many attempts to solve the CCP. Adjustment models do not avoid fine-tuning. • Higher-dimensional models of the brane-bulk type do not avoid finetuning. • Superstring theory has not yet provided a solution to the CCP. In the following, I will describe a possible resolution of the CCP, based on a model of a nonlocal field theory and quantum gravity theory that suppresses the coupling of gravity to vacuum energy density. The violation of the equivalence principle in the theory can be tested by performing Eötvos experiments on Casimir vacuum energy in satellites.