Other OHP preprints
OHP pp129 : Scintillation in scalar-tensor theories of gravity next up previous
Next: Introduction

Scintillation in scalar-tensor theories of gravity

C.Bracco 1 and P.Teyssandier 2

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.

Astronomy & Astrophysics : Received 30 July 1998/Accepted 09 september 1998


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.

Key Words : Gravitation-Relativity-Methods:Observational-Techniques:photometric

next up previous
Next: Introduction