### Abstract

We consider a toy universe containing conventional matter and an additional real scalar field, and discuss how the requirements of gauge and diffeomorphism invariance essentially single out a particular set of theories which might describe such a world at low energies. In these theories, fermion masses and g factors, as well as the electromagnetic coupling, turn out to be scalar field dependent; fermion charges and the gravitational coupling might be assumed to be constant. We then proceed to study the impact of a time variation of the scalar field on measurements of atomic spectra at high redshifts. Light propagation is not affected by a sufficiently slow change of the fine structure constant, but changes of the latter as well as variations of fermion masses and g factors do affect the observed atomic spectra. Finally, we prove the independence of these predictions on the chosen conformal frame in a further attempt to address differing views about the subject expressed in the literature.

Original language | English (US) |
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Article number | 064008 |

Pages (from-to) | 640081-640089 |

Number of pages | 9 |

Journal | Physical Review D |

Volume | 66 |

Issue number | 6 |

State | Published - Sep 15 2002 |

Externally published | Yes |

### ASJC Scopus subject areas

- Physics and Astronomy(all)
- Nuclear and High Energy Physics
- Mathematical Physics

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## Cite this

*Physical Review D*,

*66*(6), 640081-640089. [064008].