Gravitational lensing in a universe with matter and a cosmological constant

We extend the results obtained in previous works by Piattella and Park for gravitational lensing in the McVittie metric by including the effect of the transition from the matter-dominated epoch of the Universe to the Λ -dominated era. We derive a formula that agrees with the previous results for the McVittie metric at lowest order and compare the lensing angle predictions obtained from the Schwarzschild approximation, the McVittie model, and higher order corrections to the McVittie model. In doing this, we test if, beyond the correction from the accelerated expansion of the Universe, there is a need for including the matter content of the Universe in modeling lens systems at the redshifts observed in lens systems. We investigate if there is a need for a modification of the lens equation from these corrections and, if so, to which order and whether it is measurable. We find that, while the effect is of the same order as the one calculated previously, there is no significant contribution to the bending angle, as the first order effect is already of order O ( θ 4 O ) in the observed angle.