Introducing the Dirac-Milne universe
  The \Lambda CDM standard model, although an excellent parametrization of the
present cosmological data, requires two as yet unobserved components, Dark
Matter and Dark Energy, for more than 95% of the Universe. Faced to this
unsatisfactory situation, we study an unconventional cosmology, the Dirac-Milne
universe, a matter-antimatter symmetric cosmology, in which antimatter is
supposed to present a negative active gravitational mass. The main feature of
this cosmology is the linear evolution of the scale factor with time which
directly solves the age and horizon problems of a matter-dominated universe. We
study the concordance of this model to the cosmological test of Type Ia
Supernov\ae\ distance measurements and calculate the theoretical primordial
abundances of light elements for this cosmology. We also show that the acoustic
scale of the Cosmic Microwave Background naturally emerges at the degree scale
despite an open geometry.
