6. Are observational tests possible?
It follows from our formulae that the scintillation effects specifically predicted by scalar-tensor theories are proportional to the amplitude of the scalar field perturbation at the observer. This local character casts a serious doubt on the detectability of these effects, since the scalar field perturbation is very small for a localized source of gravitational waves.
Indeed, one can put in most cases , where is a dimensionless constant coupling the scalar field with the metric gravitational field (see, e.g. , Damour & Esposito-Farèse 1992). Experiments in the solar system and observations of binary pulsars like PSR 1913+16 indicate that . Consequently, setting for gravitational waves emitted by localized sources gives and the effect is much too weak to be detected.
© European Southern Observatory (ESO) 1998
Online publication: October 22, 1998