2005/01/12 by V. Folomeev, Folomeev, V., V. Gurovich +3
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0501209
8 pages, 1 figure, added reference, corrected the title of the figure
arxiv created 2005/02/03 · arxiv updated 2009/12/01
A cosmological model with a gravitational Lagrangian Lg(R)∝ R+A Rn is set up to account for the presently observed re-acceleration of the universe. The evolution equation for the scale factor a of the universe is analyzed in detail for the two parameters n=2 and n=4/3, which were preferred by previous studies of the early universe. The initial conditions are specified at a red-shift parameter z≈ 0. The fit to the observable data fixes the free parameter A. The analysis shows that the model with n=2 agrees better with present data. Then, if we set w(q)=-1 at z=0, corresponding to the deceleration parameter q≈ -1/2, we find that at z≈ 0.5, w(q) has evolved to w≈ -0.72, corresponding to q≈ 0. At z≈ 1 we find w≈ 0 corresponding to q≈ 1/2. These results are compared with the flat Friedmann model with cold matter and Lambda-term (LCDM model) for the same initial conditions at z≈ 0. The other choice of the model with n=4/3 allows for big crunch. However this possibility is eliminated by the fit of A to the present data.