DYNAMICALLY ADJUSTED COSMOLOGICAL CONSTANT AND CONFORMAL ANOMALIES

We investigate the dynamical adjustment of the cosmological constant by a "cosmic" physical scalar field φ0. We consider the quantization of general matter theories in the gravitational and φ0 backgrounds. We find that, in general, such adjustment mechanisms do not work without fine-tuning of parameters. We argue, however, that the massless Brans-Dicke coupling for φ0, where the ratio of the gravitational constant to all other mass scales is dynamical, is special: adjustment without fine-tuning may then be possible in many instances, provided a Wess-Zumino functional generated by the conformal anomaly (analog of the Liouville action in 2 dimensions) is properly included in the evaluation of the effective action. The mechanism can generate large scalar mass hierarchies. © 1990.