A new solution for inflation

Many pedagogical introductions of cosmological inflation are effective due to the simplicity of the relevant equations. Here an analytic solution of the cosmological equations is presented and used as an example to discuss fundamental aspects of the inflationary paradigm.Comment: 14 pages, LaTeX, to appear in Am. J. Phy

R^n gravity and the chameleon

The Solar System bounds on R^n gravity are often ignored in the literature by invoking the chameleon mechanism. We show that in order for the latter to work, the exponent n must be ridicolously close to unity and, therefore, these theories are severely constrained.Comment: 5 pages, latex, 1 figure, to appear in Phys. Rev.

Lemaitre model and cosmic mass

The mass of a sphere of simmetry in the Lemaitre universe is discussed using the Hawking-Hayward quasi-local energy and clarifying existing ambiguities. A covariantly conserved current introduced by Cahill and McVittie is shown to be a multiple of the Kodama energy current.Comment: 10 pages, no figures, to appear in Gen. Rel. Gravi