Abstract :
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). The interesting in this case is that the inflaton field fluctuations are related to the fifth coordinate. In power-law expansion, the fifth coordinate (ψ) appears to be a dimensionless constant. Here, 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. But the more important result here obtained is that in both cases there is not dynamical compactification during inflation.
