Artigo de Periódico
On vacuum density, the initial singularity and dark energy
Fecha
2009Registro en:
0001-7701
v. 41, n. 10
Autor
Carneiro, Saulo
Tavakol, Reza
Carneiro, Saulo
Tavakol, Reza
Institución
Resumen
Standard cosmology poses a number of important questions. Apart from
its singular origin, it possesses early and late accelerating phases required to account
for observations. The vacuum energy has been considered as a possible way to resolve
some of these questions. The vacuum energy density induced by free fields in an early
de Sitter phase has earlier been estimated to be proportional to H4,while more recently
it has been suggested that the QCD condensate induces a term proportional to H at
late times. These results have been employed in models which are non-singular and
inflationary at early times and accelerating at late times. Here we cast these models
in terms of scalar fields and study the corresponding spectrum of primordial perturbations.
At early times the spectrum is found to be not scale-invariant, thus implying that
slow-roll inflation is still required after the phase transition induced by the vacuum. At
late times the corresponding scalar-field potential is harmonic, with amass of the order of the Hubble scale, a result that may be understood in the light of the holographic
conjecture