Exploring the gamma ray horizon with the next generation of gamma ray telescopes. Part 1: Theoretical predictions

The physics potential of the next generation of gamma ray telescopes in exploring the gamma ray horizon is discussed. It is shown that a reduction in the gamma ray detection threshold might open a window to use precise determinations of the gamma ray horizon as a function of redshift to either put strong constraints on the extragalactic background light modelling or to obtain relevant independent constraints on the cosmological densities ΩM and ΩΛ.