n-point Gravitational Lenses with 5(n-1) Images

Abstract

It has been conjectured (astro-ph/0103463) that a gravitational lens consisting of n point masses can not produce more than 5(n-1) images as is known to be the case for n = 2 and 3. The reasoning is based on the number of finite limit points 2(n-1) which we believe to set the maximum number of positive images and the fact that the number of negative images exceeds the number of positive images by (n-1). It has been known that an n-point lens system (n\ge 3) can produce (3n+1) images and so has been an explicit lens configuration with (3n+1) images. We start with the well-known n-point lens configuration that produces (3n+1) images and produce (2n-1) extra images by adding a small (n+1)-th mass so that the resulting (n+1)-point lens configuration has (2n) discrete limit points and produces 5n images of a source. It still remains to confirm in abstraction that the maximum number of positive image domains of a caustic domain is bounded by the number of the limit points.