Signed magnification sums for general spherical lenses

TL;DR

This paper investigates the invariance of signed magnification sums in various spherical lens models, demonstrating their usefulness in distinguishing exotic objects like Ellis wormholes from traditional Schwarzschild lenses.

Contribution

It extends the concept of signed magnification sums to general spherical lenses, including exotic models, and shows their effectiveness in identifying different lens types.

Findings

Signed magnification sums are invariant for certain lens models.

These sums can distinguish between Schwarzschild lenses and Ellis wormholes.

The method provides a new way to identify exotic gravitational lenses.

Abstract

It is well known that the sum of signed magnifications is invariant for mass lens systems. In this paper, we discuss the signed magnification sums of general spherical lens models including the singular isothermal sphere, the Schwarzschild lens and the Ellis wormhole, the last of which is an example of the traversable wormholes of the Morris-Thorne class. We show that the signed magnication sums are a very useful tool to distinguish exotic lens objects. For example, we show that one can distinguish the Ellis wormholes from the Schwarzschild lens with the signed magnification sums.