Gravomagnetic Lensing by NUT Space

TL;DR

This paper investigates how NUT space's gravomagnetic monopoles influence gravitational lensing, revealing unique shear and spirality effects that distinguish them from standard Schwarzschild lenses.

Contribution

It demonstrates the impact of gravomagnetic monopoles on lensing patterns, introducing observable signatures like spirality and shear that are absent in traditional models.

Findings

Gravomagnetic monopoles induce shear and spirality in lensing patterns.

Lensing effects depend on the strength of the NUT parameter Q.

Results reduce to Schwarzschild lensing when Q is zero.

Abstract

Using the fact that the null geodesics in NUT space lie on spatial cones, we consider the gravomagnetic lens effect on light rays passing a NUT deflector. We show that this effect changes the observed shape, size and orientation of a source. Compared to the Schwarzschild lens, there is an extra shear (a differential twist around the lens axis) due to the gravomagnetic field which shears the shape of the source. Gravomagnetic monopoles can thus be recognized by the spirality that they produce in the lensing pattern. All the results obtained in this case (magnification factor, orientation of images, multiplicity of images, etc.) depend on $Q$, the strength of the gravomagnetic monopole represented by NUT metric. One recovers the results of the usual Schwarzschild lens effect by putting this factor equal to zero.