Inflation by non-minimal coupling

Inflationary scenarios based on simple non-minimal coupling aφ2R and its generalizations are studied. First, generalizing the form of non-minimal coupling to K(φ)R with an arbitrary function K, we show that the flat potential still is obtainable when V (φ)/K2(φ) is asymptotically constant. Very interestingly, if the ratio of the dimensionless quartic coupling(λ) of the inflaton field and the non-minimal coupling constant (a) is small, √ λ/a2 ∼ 10−5, the cosmological observables for general monomial cases (K ∼ aφm) are in good agreement with recent observational data. Embedding to higher dimensional spacetime (D ≥ 4), we show that the large volume compactification with ML ∼ 10 9 D−4 can be responsible for the smallness of √ λ/a2.