Gravitational lensing shear by an exotic lens object with negative convergence or negative mass
Abstract
Gravitational lens models with negative convergence (surface mass density projected onto the lens plane) inspired by modified gravity theories, exotic matter, and energy have been recently discussed in such a way that a static and spherically symmetric modified spacetime metric depends on the inverse distance to the power of positive n (n=1 for Schwarzschild metric, n=2 for Ellis wormhole) in the weakfield approximation [T. Kitamura, K. Nakajima, and H. Asada, Phys. Rev. D 87, 027501 (2013)], and it has been shown that demagnification of images could occur for n>1 lens models associated with exotic matter (and energy), though they cause the gravitational pull on light rays. The present paper considers gravitational lensing shear by the demagnifying lens models and other models such as negativemass compact objects causing the gravitational repulsion on light rays like a concave lens. It is shown that images by the lens models for the gravitational pull are tangentially elongated, whereas those by the repulsive ones are radially distorted. This feature of lensed image shapes may be used for searching (or constraining) localized exotic matter or energy with gravitational lensing surveys. It is suggested also that an underdense region such as a cosmic void might produce radially elongated images of background galaxies rather than tangential ones.
 Publication:

Physical Review D
 Pub Date:
 July 2013
 DOI:
 10.1103/PhysRevD.88.024049
 arXiv:
 arXiv:1305.5037
 Bibcode:
 2013PhRvD..88b4049I
 Keywords:

 04.40.b;
 95.30.Sf;
 98.62.Sb;
 Selfgravitating systems;
 continuous media and classical fields in curved spacetime;
 Relativity and gravitation;
 Gravitational lenses and luminous arcs;
 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 15 pages, 4 figures. derivation of lensing shear is clarified. accepted by PRD. arXiv admin note: text overlap with arXiv:1211.0379