Exact Inflationary Solution to Nonminimally Coupled Scalar Field

We present a new exact inflationary solution to nonminimally coupled scalar field. The inflation is driven by the evolution of scalar field with inflation potential V(λ) =λ /4 ψ⁴ - 1/2m² ψ ² + V₀. This includes the solution that behaves exponential inflation for ψ₀ > ψ > ψ_end and then develops smoothly towards radiation-like evolution for ψ < ψ_end. The spectral index of the scalar density fluctuations, n_s, is computed, and the result is consistent with the analysis of the Wilkinson-microwave anisotropy probe data. This model can lead to successful inflation with approx 10^-7, rather than 10^-13 reported previously.