2006/03/08 by Iver Brevik · 1 citation
Physics and Astronomy · #gr-qc #astro-ph #hep-th
paper · pdf · doi:10.1007/s10714-006-0309-y
published as Gen.Rel.Grav.38:1317-1328,2006 · 16 pages latex, no figures
arxiv created 2006/03/08 · arxiv updated 2009/12/01
Singularities in the dark energy late universe are discussed, under the assumption that the Lagrangian contains the Einstein term R plus a modified gravity term of the form Rα, where αis a constant. It is found, similarly as in the case of pure Einstein gravity [I. Brevik and O. Gorbunova, Gen. Rel. Grav. 37 (2005), 2039], that the fluid can pass from the quintessence region (w>-1) into the phantom region (w<-1) as a consequence of a bulk viscosity varying with time. It becomes necessary now, however, to allow for a two-fluid model, since the viscosities for the two components vary differently with time. No scalar fields are needed for the description of the passage through the phantom barrier.