Caustics of 1/r^{n} binary gravitational lenses: from galactic haloes to exotic matter
Abstract
We investigate the caustic topologies for binary gravitational lenses made up of two objects whose gravitational potential declines as 1/r^{n}. With n<1 this corresponds to powerlaw dust distributions like the singular isothermal sphere. The n>1 regime can be obtained with some violations of the energy conditions, one famous example being the Ellis wormhole. Gravitational lensing provides a natural arena to distinguish and identify such exotic objects in our Universe. We find that there are still three topologies for caustics as in the standard Schwarzschild binary lens, with the main novelty coming from the secondary caustics of the close topology, which become huge at higher n. After drawing caustics by numerical methods, we derive a large amount of analytical formulae in all limits that are useful to provide deeper insight in the mathematics of the problem. Our study is useful to better understand the phenomenology of galaxy lensing in clusters as well as the distinct signatures of exotic matter in complex systems.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 March 2016
 DOI:
 10.1088/14757516/2016/03/040
 arXiv:
 arXiv:1511.07991
 Bibcode:
 2016JCAP...03..040B
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 28 pages, 19 figures, focus expanded to galactic haloes