Abstract. We study the present, flat isotropic universe in 1/R-modified gravity. We use the Palatini (metric-affine) variational principle and the Einstein (metric-compatible connected) conformal frame. We show that the energy density scaling deviates from the usual scaling for nonrelativistic matter, and the largest deviation occurs in the present epoch. We find that the current deceleration parameter derived from the apparent matter density parameter is consistent with observations. There is also a small overlap between the predicted and observed values for the redshift derivative of the deceleration parameter. The predicted redshift of the deceleration-to-acceleration transition agrees with that in the ΛCDM model but it is larger than the value estimated from SNIa observations.

PACS numbers: 04.50.-h, 98.80.−k

Print publication: Issue 15 (7 August 2006)
Received 22 January 2006, in final form 23 June 2006
Published 6 July 2006