Inflationary cosmology from STM theory of gravity

I study the power-law and de Sitter expansions for the universe during inflation from the STM theory of gravity. In a de Sitter expansion the additional dimension is related to the cosmological constant Λ = 3/ψ2. I find from experimental data that the mass of the inflaton field is m2 = 2/(3ψ2). In power-law expansion, the fifth coordinate (ψ) appears to be a dimensionless constant. The interesting here is that the ψ-value depends on the initial conditions. I find the 5D line element for this inflationary expansion, which is a function of the classical component of the inflaton. Pacs numbers: 98.80.Cq, 04.20.Jb, 11.10.kk