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3.6. The amount of inflation

The amount of inflation is normally specified by the logarithm of the amount of expansion, the number of e-foldings N, given by

Equation 32 (32)

where the final step uses the SRA. Notice that the amount of inflation between two scalar field values can be calculated without needing to solve the equations of motion, and also that it is unchanged if one multiplies V(phi) by a constant.

The minimum amount of inflation required to solve the flatness and horizon problems is about 70 e-foldings, i.e. an expansion by a factor of about 1030. Although this looks large, inflation is typically so rapid that most inflation models give much more.