An Alternative to the ΛCDM Model: The Case of Scale Invariance
Abstract
The hypothesis is made that, at large scales where general relativity may be applied, empty space is scale invariant. This establishes a relation between the cosmological constant and the scale factor λ of the scaleinvariant framework. This relation brings major simplifications in the scaleinvariant equations for cosmology, which contain a new term, depending on the derivative of the scale factor, that opposes gravity and produces an accelerated expansion. The displacements due to the acceleration term make a high contribution {{{Ω }}}_{λ } to the energy density of the universe, satisfying an equation of the form {{{Ω }}}_{{{m}}}+{{{Ω }}}_{{{k}}}+{{{Ω }}}_{λ }=1. The models do not demand the existence of unknown particles. There is a family of flat models with different density parameters {{{Ω }}}_{{{m}}}< 1. Numerical integrations of the cosmological equations for different values of the curvature and density parameter k and {{{Ω }}}_{{{m}}} are performed. The presence of even tiny amounts of matter in the universe tends to kill scale invariance. The point is that for {{{Ω }}}_{{{m}}}=0.3 the effect is not yet completely killed. Models with nonzero density start explosively with a braking phase followed by a continuously accelerating expansion. Several observational properties are examined, in particular the distances, the mz diagram, and the {{{Ω }}}_{{{m}}} versus {{{Ω }}}_{λ } plot. Comparisons with observations are also performed for the Hubble constant H_{0} versus {{{Ω }}}_{{{m}}}, for the expansion history in the plot H(z)/(z+1) versus redshift z, and for the transition redshift from braking to acceleration. These first dynamical tests are satisfied by scaleinvariant models, which thus deserve further study.
 Publication:

The Astrophysical Journal
 Pub Date:
 January 2017
 DOI:
 10.3847/15384357/834/2/194
 arXiv:
 arXiv:1701.03964
 Bibcode:
 2017ApJ...834..194M
 Keywords:

 cosmology: theory;
 dark energy;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 16 pages, 10 figures