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. I find from
experimental data that the mass of the inflaton field is m2=2/(3Ψ2). In
power-law expansion, the fifth coordinate 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.Comment: final versio