caa a22 4500 467886687 CHVBK 20180406152736.0 cr unu---uuuuu 170328e20060101xx s 000 0 eng 10.1007/s10714-005-0209-6 doi (NATIONALLICENCE)springer-10.1007/s10714-005-0209-6 de Leon J. Department of Physics, Laboratory of Theoretical Physics, University of Puerto Rico, P.O. Box 23343, 00931, Rio Piedras, PR, USA aut Transition from decelerated to accelerated cosmic expansion in braneworld universes [Elektronische Daten] [J. de Leon] Braneworld theory provides a natural setting to treat, at a classical level, the cosmological effects of vacuum energy. Non-static extra dimensions can generally lead to a variable vacuum energy, which in turn may explain the present accelerated cosmic expansion. We concentrate our attention in models where the vacuum energy decreases as an inverse power law of the scale factor. These models agree with the observed accelerating universe, while fitting simultaneously the observational data for the density and deceleration parameter. The redshift at which the vacuum energy can start to dominate depends on the mass density of ordinary matter. For $$\bar \Omega$$ m = 0.3, the transition from decelerated to accelerated cosmic expansion occurs at z T ≈ 0.48 ± 0.20, which is compatible with SNe data. We set a lower bound on the deceleration parameter today, namely $$\bar{q}$$ > − 1 + 3 $$\bar \Omega$$ m /2, i.e., $$\bar{q}$$ > − 0.55 for $$\bar \Omega $$ m = 0.3. The future evolution of the universe crucially depends on the time when vacuum starts to dominate over ordinary matter. If it dominates only recently, at an epoch z < 0.64, then the universe is accelerating today and will continue that way forever. If vacuum dominates earlier, at z > 0.64, then the deceleration comes back and the universe recollapses at some point in the distant future. In the first case, quintessence and Cardassian expansion can be formally interpreted as the low energy limit of our model, although they are entirely different in philosophy. In the second case there is no correspondence between these models and ours. Springer-Verlag, 2005 Cosmic accelerated expansion nationallicence Brane theory nationallicence Cosmology: theory nationallicence Variable fundamental constants nationallicence Cardassian expansion nationallicence Dark matter nationallicence General Relativity and Gravitation Springer US; http://www.springer-ny.com 38/1(2006-01-01), 61-81 0001-7701 38:1<61 2006 38 10714 https://doi.org/10.1007/s10714-005-0209-6 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10714-005-0209-6 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- de Leon J. Department of Physics, Laboratory of Theoretical Physics, University of Puerto Rico, P.O. Box 23343, 00931, Rio Piedras, PR, USA aut NATIONALLICENCE 773 0- General Relativity and Gravitation Springer US; http://www.springer-ny.com 38/1(2006-01-01), 61-81 0001-7701 38:1<61 2006 38 10714 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer