A particular example of a Morris-Thorne wormhole is the Ellis wormhole [102] where
with a constantLensing by the Ellis wormhole was discussed
in [55]; in this paper the
authors identified the region with the
region
and they developed a scattering
formalism, assuming that observer and light source are in the
asymptotic region. Lensing by the Ellis wormhole was also discussed
in [271
] in terms of the
exact lens map. The resulting features are qualitatively very
similar to the Schwarzschild case, with the radius values
,
,
in the wormhole
case corresponding to the radius values
,
,
in the Schwarzschild case. With this
correspondence, Figures 15
, 16
, and 17
qualitatively
illustrate lensing by the Ellis wormhole. More generally, the same
qualitative features occur whenever the metric function
has one minimum and no other extrema, as in
Figure 9
.
If observer and light source are on the same side
of the wormhole’s neck, and if only light rays in the asymptotic
region are considered, lensing by a wormhole can be studied in
terms of the quasi-Newtonian approximation formalism [182]. However, as
wormholes are typically associated with negative energy
densities [227, 228], the usual
assumption of the quasi-Newtonian approximation formalism that the
mass density is positive cannot be maintained. This observation has
raised some interest in lensing by negative masses, in particular
in the question of whether negative masses can be detected by their
(“microlensing”) effect on the energy flux from sources passing
behind them. So far, related calculations [64, 293] have been done
only in the quasi-Newtonian approximation formalism.