## Scintillation in scalar-tensor theories of gravity
^{1} Observatoire de Haute-Provence, CNRS, F-04870
Saint-Michel l'Observatoire, France^{2} Laboratoire de Gravitation et Cosmologie Relativistes,
Université Pierre et Marie Curie, CNRS/ESA 7065, Tour 22/12, BP
142, 4 place Jussieu, F-75252 Paris Cedex 05, France
We study the scintillation produced by time-varying gravitational fields within scalar-tensor theories of gravity. The problem is treated in the geometrical optics approximation for a very distant light source emitting quasi plane monochromatic electromagnetic waves. We obtain a general formula giving the time dependence of the photon flux received by a freely falling observer. In the weak-field approximation, we show that the contribution to the scintillation effect due to the focusing of the light beam by a gravitational wave is of first order in the amplitude of the scalar perturbation. Thus scalar-tensor theories contrast with general relativity, which predicts that the only first-order effect is due to the spectral shift. Moreover, we find that the scintillation effects caused by the scalar field have a local character: they depend only on the value of the perturbation at the observer. This effect provides in principle a mean to detect the presence of a long range scalar field in the Universe, but its smallness constitutes a tremendous challenge for detection.
This article contains no SIMBAD objects. ## Contents- 1. Introduction
- 2. Notations and definitions
- 3. General theory of the gravitational scintillation
- 4. Weak-field approximation
- 5. Application to the scalar-tensor theories
- 6. Are observational tests possible?
- Acknowledgements
- References
© European Southern Observatory (ESO) 1998 Online publication: October 22, 1998 |