Takao Kitamura, Koki Nakajima, Hideki Asada
We examine a gravitational lens model inspired by modified gravity theories, exotic matter and energy. We study an asymptotically flat, static and spherically symmetric spacetime that is modified in such a way that the spacetime metric depends on the inverse distance to the power of positive n in the weak field approximation. It is shown analytically and numerically that demagnifying gravitational lenses could appear, provided the impact parameter of light $\beta$ and the power n satisfy $\beta > 2/(n+1)$ in the units of the Einstein ring radius. Unusually, the total amplification of the lensed images, though they are caused by the gravitational pull, could be less than the unity. Therefore, time-symmetric extinction parts in numerical light curves by gravitational microlensing (Abe, Astrophys. J. 725, 787, 2010) may be an evidence of an Ellis wormhole (being an example of traversable wormholes) but they do not always prove it. Such a gravitational extinction of the light might be used for hunting a clue of exotic matter and energy that are described by an equation of state more general than the Ellis wormhole case. Numerical calculations for n=3 and 10 cases show $\sim 10$ and $\sim 60$ percent depletion of the light, respectively.
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http://arxiv.org/abs/1211.0379
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