Gravity balls in induced gravity model - 'gravitational lens' effects

Abstract

In non-minimally coupled effective gravity theories one can have non-topological solitonic solutions. A typical solution is a spherical region with $G_{\it eff}=0$ outside and having the canonical Newtonian value inside. Such a spherical domain (gravity-ball) is characterized by an effective index of refraction which causes bending of light incident on it. The gravity ball thus acts as a spherical lens. We consider the gravity ball to be of a size of a typical cluster of galaxies and show that even empty (without matter) gravity ball can produce arc-like images of the background source galaxy. In case of background random galaxy field the ball produces distortions (`shear') of that field. We also obtained constraints on the size of the large gravity ball, which can be inferred from the existing observations of clusters with arcs.