Constant From Gravitational Lenses In An Evolutionary Model Of Galaxies

We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (Ω0 + λ0 = 1). It is shown that some of the lens observables are strongly affected by the cosmological constant, especially in a low–density universe, and its existence might be inferred by a statistical study of the lenses. In particular, the optical depth of the lens distribution may be used best for this purpose without depending much on the lens model. We calculate the optical depth (probabilty of a beam encountering with a lens event) for a source in a new picture of galaxy evolution based on number evolution in addition to pure luminosity evolution. It seems that present day galaxies result from the merging of a large number of building blocks. We have tried to put limit on the cosmological E–mail : [email protected] E–mail : [email protected] E–mail : [email protected] E–mail : [email protected]