Towards a new proposal for the time delay in gravitational lensing
  One application of the Cosmological Gravitational Lensing in General
Relativity is the measurement of the Hubble constant H_0 using the time delay
Delta t between multiple images of lensed quasars. This method has already been
applied, obtaining a value of H_0 compatible with that obtained from the SNe
1A, but non compatible with that obtained studying the anisotropies of the CMB.
This difference could be a statistical fluctuation or an indication of new
physics beyond the Standard Model of Cosmology, so it desirable to improve the
precision of the measurements. At the current technological capabilities it is
possible to obtain H_0 to a percent level uncertainty, so a more accurate
theoretical model could be necessary in order to increase the precision about
the determination of H_0. The actual formula which relates Delta t with H_0 is
approximated; in this paper we expose a proposal to go beyond the previous
analysis and, within the context of a new model, we obtain a more precise
formula than that present in the Literature.
