Choosing a Conformal Frame in Scalar-Tensor Theories of Gravity with a Cosmological Constant
Abstract
Cosmological solutions of the Brans-Dicke theory with an added cosmological constant are investigated with an emphasis on selecting a conformal frame in order to implement the scenario of a decaying cosmological constant, featuring an ever-growing scalar field. We focus particularly on the Jordan frame, the original frame with nonminimal coupling, and the conformally transformed Einstein frame without it. For the asymptotic attractor solutions as well as the `hesitation behavior', we find that none of these conformal frames can be accepted as the basis of analyzing primordial nucleosynthesis. As a remedy, we propose to modify the prototype BD theory by introducing a scale-invariant scalar-matter coupling, thus making the Einstein frame acceptable. The invariance is broken as a quantum anomaly effect due to non-gravitational interactions, naturally entailing a fifth force, characterized by a finite force-range and violation of weak equivalence principle (WEP). A tentative estimate shows that the theoretical prediction is roughly consistent with the observational upper bounds. Further efforts to improve experimental accuracy are strongly encouraged.
- Publication:
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Progress of Theoretical Physics
- Pub Date:
- April 1998
- DOI:
- 10.1143/PTP.99.599
- arXiv:
- arXiv:gr-qc/9708010
- Bibcode:
- 1998PThPh..99..599F
- Keywords:
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- General Relativity and Quantum Cosmology
- E-Print:
- Latex 29 pages, including 9 figures