Non minimally coupled inflation

Non-minimally coupled inflation is an inflationary model in which the constant which couples gravity to the inflaton field is not small. The coupling constant is usually represented by ξ (Xi), which features in the action (constructed by modifying the Einstein–Hilbert action):

S = ∫ d 4 x − g [ m P 2 2 R − 1 2 ∂ μ ϕ ∂ μ ϕ − V ( ϕ ) − ξ 2 R ϕ 2 ]

ξ represents the strength of the interaction between R and ϕ , which relate to the curvature of space and the magnitude of the inflaton field respectively.